Search

Toxoplasmosis is an important cause of congenital infection. The present study was performed to evaluate the usefulness of recombinant (r) GRA-7 cloned from nucleotides (n) 39-711 in discriminating between acute and chronic toxoplasmosis. First, commercial IgM, IgG and IgG avidity ELISAs were used to determine the serological profile of the sera. Serum samples were from 20 symptomatic patients with acute infection (low IgG avidity, IgM positive), 10 with chronic infection (high IgG avidity, IgM negative) and 10 with indeterminate IgG avidity (IgM positive) which were tested for IgG avidity status with an in-house developed IgG avidity Western blot using the rGRA-7 recombinant antigen. All 20 sera from cases of probable acute infection showed bands which either faded out completely or reduced significantly in intensity after treatment with 8 M urea, whereas the band intensities of the 10 serum samples from chronic cases remained the same. Of the 10 sera with indeterminate IgG avidity status, after treatment with 8 M urea the band intensities with six sera remained the same, two sera had completely faded bands and another two sera had significantly reduced band intensities. Discrimination between acute and chronic toxoplasmosis was successfully performed by the in-house IgG avidity Western blot. Toxoplasmose é uma causa importante de infecção congênita. O presente estudo foi feito para avaliar o uso do recombinante (r) GRA-7 clonado de nucleotídeos (n) 30-711 para discriminar entre toxoplasmose aguda e crônica. Inicialmente IgM, IgG e ELISA avidez IgG comerciais foram usados para determinar o perfil sorológico do soro. Amostras de soro de 20 pacientes sintomáticos com infecção aguda (IgG avidez baixa, IgM positivo), 10 com infecção crônica (alta avidez IgG, IgM negativo) e 10 com avidez IgG indeterminada (IgM positivo) que foram testados para o status de avidez IgG com um doméstico Western Blot desenvolvendo avidez IgG usando o rGRA-7 antígeno recombinante. Todos os 20 soros de provável infecção aguda mostraram bandas que ou se apagaram completamente ou tiveram a sua intensidade significantemente reduzida após tratamento com uréia 8 M, enquanto as intensidades das bandas das 10 amostras de soros de casos crônicos permaneceram iguais. Dos 10 soros com status indeterminado de avidez de IgG, após tratamento com uréia 8 M a intensidade das bandas em seis soros permaneceram iguais, dois soros tiveram bandas apagadas completamente e dois outros tiveram significante redução da intensidade das bandas. Discriminação entre toxoplasmose aguda e crônica foi feita com sucesso através do IgG avidez Western blot doméstico.

この研究は, Porpgyromonas gingivalisの表層抗原に対する成人性歯周炎患者血清中のIgG抗体のアビディティについて検討したものである。抗原として組織侵襲性の低いP. gingivalis ATCC 33277株と組織侵襲性の高い16-1株の, 全菌体, 抽出したリポ多糖 (LPS) および線毛抗原を用いた。血清IgG抗体価は, 初期治療前と初期治療後に, 酵素免疫測定法 (ELISA) によって調べた。IgGアビディティ力価はdiethylamineを用いたELISAで測定した。治療前の患者群の血清IgG抗体は, 16-1株全菌体抗原, 両菌株のP. gingivalis抽出LPSと線毛抗原に対して, 健常者群と比較して, 高いIgG抗体価を示したが, そのアビディティ力価は低かった。しかしながら, 治療後に患者群の血清IgG抗体価は有意に減少し, 16-1株線毛抗原に対するIgGアビディティ力価は有意に増加した。本研究では成人性歯周炎患者の血清IgG抗体は, 組織侵襲性の低いATCC 33277株より組織侵襲性の高い16-1株に対して, より鋭敏な反応を示すことを明らかにした。患者群のIgG抗体価は高いものの, そのアビディティ力価が低く, Pgingivalisの感染を十分に抑制, 排除できないと思われる。健常者群では機能的なIgG抗体がP. gingivalisの感染を防御していることを示唆した。また初期治療によって成人性歯周炎患者では, より機能的なIgG抗体の産生が導かれる可能性を示した。

The serodiagnosis of human toxocariasis is difficult. Specific IgGs detected routinely with ELISA based on Toxocara excretory-secretory (TES) antigens often persist for years at an elevated level, which does not allow either the differentiation between an active and persistent infection or monitoring the effect of treatment. Additionally, false positive results may occur in co-infections with other helminths due to cross-reactions. We evaluated the usefulness of an IgG avidity index (AI) and a Western blotting (WB) IgG in the diagnosis of patients suspected of Toxocara infection. We studied 138 subjects who were submitted to serological testing two or more times. Confirmation of an infection by WB was achieved in 73.2% of patients. A high AI was obtained in 89.1% of patients, and low AI and borderline AI were found in only 10.9%. Low and borderline values of AI remained at similar levels in subsequent studies over 2-3 years. The results showed the necessity of obligatory verification of all ELISA IgG positive and questionable results by WB. The index of IgG avidity may be helpful in excluding recent infection, but its usefulness in detecting an active phase of invasion requires further research. This article is protected by copyright. All rights reserved.

An enzyme-linked immunosorbent assay-based immunoglobulin G (IgG) antibody avidity test was evaluated by using sera from 57 patients with acute dengue infection. Overall, 55 of 57 patients were correctly classified (27 of 27 with primary dengue and 28 of 30 with secondary dengue). We conclude that the IgG avidity test can be useful for differentiating between acute, primary, and secondary dengue infections.

Serological screening for maternal Toxoplasma infections in pregnancy has been questioned recently. We analyze some diagnostic difficulties for routine laboratories, poor public health guidance of existing screening programs, and their mutual worsening impact on the efficacy of the programs and on toxoplasmosis research. False positive screening tests may be more likely than true maternal Toxoplasma infections and diagnosis often depends on confirmatory testing in experienced reference laboratories. Apart from clear seroconversions, any marker to assign the time point of infection to the ongoing pregnancy (IgM, IgG avidity, etc.) suffers from important limitations. With poor screening compliance, many screening alerts come from first serum samples in pregnancy that are cumbersome to test, while seroconversions are seldom observed due to missing follow-up samples in late pregnancy. From a public health perspective, inadequate epidemiological assessment and research, insufficient quality control for compliance and little consideration of diagnostic peculiarities for the design of more effective preventive programs has resulted in poor performance. These shortcomings have contributed to the present doubts about preventive Toxoplasma screening in pregnancy. We recommend that a team of public health decision makers, epidemiologists and experts from toxoplasmosis reference laboratories reevaluates the existing activities in a given country to build up a well-designed preventive program that avoids these drawbacks.

O objetivo deste estudo foi avaliar o valor preditivo do teste de avidez de IgG no diagnóstico precoce da toxoplasmose congênita (TC) no recém-nascido (RN). O grupo de estudo foi constituído por 68 pares de puérperas e seus RN, sendo 43 com toxoplasmose aguda durante a gravidez e 25 com IgM negativo para Toxoplasma gondii (grupo controle). As pacientes pariram os RN na Maternidade do Hospital das Clínicas da Universidade Federal de Goiás. Foram avaliados os níveis séricos de IgM e IgG anti-T. gondii e avidez de IgG. Os RN do grupo de estudo foram divididos em RN com baixa avidez (BA) e RN com elevada avidez (EA). Foi verificada a concordância do teste de avidez dos RN e das puérperas. A infecção pelo T. gondii foi observada em 94,1% dos RN com BA e 42,3% dos RN com EA. Os níveis de IgG e de IgM dos RN com BA e de suas puérperas infectadas foram elevados e apresentaram diferença quando comparados com os RN com EA (p=0,0001) e os RN não infectados (p=0,0001) e suas respectivas puérperas. A sintomatologia da TC foi observada em 56% dos RN com BA e em 18% dos RN com EA. Nossos dados mostram que RN com BA apresentaram aumento de IgM e IgG e sintomas severos da TC. Assim, o teste de avidez poderia ser utilizado em conjunto com a detecção de IgM e IgG no diagnóstico precoce da TC no RN.

To evaluate the incidence of Toxoplasma gondii infection, the detection of specific IgG, IgM, IgA and IgG avidity was performed on 1424 pregnant women referred to the “L. Spallanzani” Hospital in Rome (Italy). Of the 1424 women screened, 20 (1.40%) were likely to have been recently infected (presence of IgM/IgA, and/or low IgG avidity), 29 (2.04%) had positive IgM coupled with high IgG avidity, 7 (0.49%) had an unspecific result for IgM alone, 1339 (94.0%), were negative for both IgG and IgM, 29 (2.04%) showed evidence of past infection (IgG positive, IgM negative, high IgG avidity). In Conclusion our results underscore the importance of efficient antenatal screening and appropriate treatment for Toxoplasma infection in Italy.

We used maternal immunoglobulin M (IgM), immunoglobulin G (IgG) avidity index (AI) and fetal ultrasonography (US) to effectively detect a congenital cytomegalovirus-infected fetus that would suffer neurological sequelae after birth.The detecting method was prospectively adapted to 1163 unselected pregnant women. IgM, IgG and IgG-AI were measured at the first prenatal examination (10.8±2.2 weeks of gestation). Advanced US was performed for the IgM-positive women at our center. The urine of 1163 neonates was examined via PCR. All infected neonates were followed for neurological development.Most women (83.3%) were seropositive. Among them, 40 (4.1%) were IgM positive. Nine of forty (22.5%) had low AI, of which one showed abnormal US and suffered severe sequelae. The remaining eight had a normal US; however, one infant had hearing impairment. There were another three infected infants with normal development. Their mothers' serological results were: IgM positive with high AI (n=1); IgG positive; IgM negative with high AI (n=1); and both IgG and IgM negative (n=1).This method enabled us to detect infected fetuses having severe sequelae. However, the problem remains of detecting infected fetuses that only have a hearing impairment.

Epstein-Barr virus (EBV), öncelikle enfeksiyöz mononükleoz ve ayrıca çeşitli lenfomalar ve posttransplant lenfoproliferatif hastalığın (PTLD) etiyolojisinden sorumlu, latent enfeksiyon oluşturan bir herpes virustur. EBV enfeksiyonlarının laboratuvar tanısı; atipik lenfositlerin, heterofil antikorların, virusun kapsid antijeni (VCA), nükleer antijeni (EBNA) ve erken antijeni (EA)'ne karşı oluşan özgül antikorların ve viral DNA'nın saptanmasına dayanır. Ülkemizde yetişkin popülasyondaki seropozitiflik oranının çok yüksek (%80-95) olması nedeniyle, transplant alıcıları veya onkoloji hastaları gibi özellikle immünsüpresif hasta gruplarında EBV reaktivasyonunun belirlenmesinde rutin serolojik testler yetersiz kalabilir. Bu gibi durumlarda VCA IgG avidite testi ve moleküler yöntemlerden yararlanılmaktadır. Bu çalışmada, renal transplant ve çocuk onkoloji hastalarında EBV enfeksiyonlarının tanı ve takibinde serolojik yöntemlerin yanı sıra gerçek zamanlı polimeraz zincir reaksiyonu (Rt-PCR) ile viral DNA düzeylerinin belirlenmesi amaçlanmıştır. Çalışmaya, 62 erişkin renal transplant alıcısı, 37 çocuk onkoloji hastası ile EBV seropozitif immün kompetan sağlıklı 50 birey (28'i çocuk, 22'si erişkin) dahil edilmiştir. Transplant alıcılarından transplantasyon öncesi bir kez, transplantasyon sonrası üç kez (birinci hafta, birinci ay ve üçüncü ay) olmak üzere toplam dört kez; çocuk onkoloji hastalarından tedavi öncesi bir kez, immünsüpresif tedaviye başlandıktan sonra üç kez (birinci ay, üçüncü ay ve altıncı ay) olmak üzere toplam dört kez; kontrol grubundan ise bir kez kan örneği alınmıştır. Serum örneklerinde EBV serolojik profilleri Paul-Bunnel ve immünoblot testleri ile; VCA IgG avidite testi ELISA ile ve EBV-DNA düzeyi Rt-PCR yöntemiyle araştırılmıştır. Renal transplant grubundaki hastaların 3 (%4.8)'ünde EBV-DNA pozitif bulunmuştur. Bu hastalarda CD4/CD8 oranları transplantasyon öncesi değerlerine göre transplantasyon sonrası birinci hafta ve üçüncü ayda anlamlı olarak düşük bulunmakla birlikte PTLD ve organ reddi gelişmemiştir. Çocuk onkoloji grubundaki hastaların 3 (%8.1)'ünde EBV-DNA pozitif bulunmuş; bu durum Hodgkin lenfoma tanısıyla takip edilen iki çocukta hastalık, diğerinde ise reaktivasyon ile ilişkilendirilmiştir. Kontrol grubundaki olguların ise 10 (%20)'unda EBV-DNA pozitifliği tespit edilmiştir. İmmünoblot sonuçları akut enfeksiyon serolojisi ile uyumlu olan erişkin kontrol olgularında EBV-DNA pozitifliği, Paul-Bunnel pozitifliği ve düşük avidite sonuçları arasındaki uyum istatistiksel olarak anlamlıdır. Çocuk kontrol grubunda ise bu serolojik profil ile sadece düşük avidite arasındaki uyum anlamlı kabul edilmiştir. Sonuç olarak bu çalışmada erişkin renal transplant hastalarında transplantasyonu takip eden üç aylık dönemde EBV ile ilişkili PTLD ve akut rejeksiyon riskinin bulunmadığı; EBV ile ilişkili malignitesi bulunan çocuklarda tedavi öncesi Rt-PCR ile EBV-DNA araştırılmasının tanı, takip ve prognozu değerlendirmede yararlı olabileceği; immünsüpresif hastalarda EBV reaktivasyonunu saptamak için serolojik sonuçların avidite ve PCR testleri ile desteklenmesi gerektiği düşünülmüştür. Epstein-Barr virus (EBV), a herpesvirus leading to latent infections, is principally responsible for infectious mononucleosis, and also plays role in the etiology of various lymphomas and post-transplantation lymphoproliferative disease (PTLD). Laboratory diagnosis of EBV infections depends on the detection of atypical lymphocytes, heterophile antibodies, specific antibodies against viral capsid (VCA), nuclear (EBNA) and early (EA) antigens, and of the viral DNA. Since the seropositivity rate in adult population is very high (80-95%) in our country, routine serologic tests may be insufficient to characterize EBV reactivation in immunosuppressive subjects, such as transplant recipients or oncology patients. In those cases VCA IgG avidity test and molecular methods are more useful. This study was conducted to determine the role of viral DNA levels detected by real-time polymerase chain reaction (Rt-PCR) and serological tests for the diagnosis and follow up of EBV infections in renal transplant recipients and pediatric oncology patients. A total of 62 adult renal transplant recipients, 37 children with oncological diseases, and 50 EBV-seropositive immunocompetent healthy subjects (28 children, 22 adults) as controls, were included in the study. Four blood samples, once before transplantation and three times thereafter (at first week, first and third months) were collected from transplant recipients; in pediatric oncology patients blood samples were collected four times, once before immunosuppressive treatment and three times thereafter (at first, third and sixth months), while the control group had a single blood sample collected. Serological profiles for EBV were searched by Paul-Bunnel and immunoblotting tests; VCA IgG avidity by ELISA and viral load by Rt-PCR. EBV-DNA was found positive in 3 (4.8%) of the renal transplant patients. While in these patients the CD4/CD8 ratio was significantly lowered in the first week and third month post-transplant, no PTLD or organ rejection developed. EBV-DNA was positive in 3 (8.1%) of the pediatric oncology patients. This positivity was attributed to Hodgkin's disease in two of these cases and to reactivation in the third case. EBV-DNA positivity was present in 10 (20%) of the control subjects. In the adult controls whose immunoblot results were compatible with the serologic pattern of an acute infection, the correlation among positive EBV-DNA, positive Paul-Bunnel and low IgG avidity results was statistically significant. As for children in the control group, this serologic profile was significantly correlated with low IgG avidity only. The data obtained from this study indicated that no risk of EBV-related PTLD or acute rejection was found in the first three months in the adult renal transplant patients. In children with EBV-related malignancy the search for EBV-DNA by RtPCR before therapy may be useful in the diagnosis, follow-up and prognostic evaluation. Serologic results should be supported by IgG avidity and PCR in order to ascertain the presence of EBV reactivation in immunosuppressive patients.

Foodborne diseases represent operational risks in industrial restaurants. We described an outbreak of nine clustered cases of acute illness resembling acute toxoplasmosis in an industrial plant with 2300 employees. These patients and another 36 similar asymptomatic employees were diagnosed with anti-T. gondii IgG titer and avidity by ELISA. We excluded 14 patients based on high IgG avidity and chronic toxoplasmosis: 13 from controls and one from acute disease other than T. gondii infection. We also identified another three asymptomatic employees with T.gondii acute infection and also anti-T. gondii IgM positive as remaining acute cases. Case control study was conducted by interview in 11 acute infections and 20 negative controls. The ingestion of green vegetables, but not meat or water, was observed to be associated with the incidence of acute disease. These data reinforce the importance of sanitation control in industrial restaurants and also demonstrate the need for improvement in quality control regarding vegetables at risk for T. gondii oocyst contamination. We emphasized the accurate diagnosis of indexed cases and the detection of asymptomatic infections to determine the extent of the toxoplasmosis outbreak. Doenças transmitidas por alimentos representam riscos operacionais em restaurantes industriais. Descrevemos surto de nove casos agrupados de doença aguda semelhante à toxoplasmose em indústria de 2300 funcionários. Estes pacientes e outros 36 funcionários assintomáticos foram diagnosticados por ELISA para o título e avidez de IgG anti-T. gondii. Foram excluídos 14 pacientes com toxoplasmose crônica e alta avidez: 13 de controles e um de doença aguda não relacionada à infecção por T. gondii. Também identificamos três empregados assintomáticos com infecção aguda por T.gondii, que como os restantes agudos apresentavam anti-T.gondii IgM ELISA positivo. Conduzimos estudo caso controle por entrevista em 11 infecções agudas e 20 controles negativos. A ingestão de vegetais, mas não de carne ou água, foi associada com a incidência da doença aguda. Esses dados reforçam a importância do controle sanitário em restaurantes industriais e também demonstram a necessidade de melhoria no controle de qualidade sobre vegetais em risco de contaminação por oocistos de T. gondii. Enfatizamos o diagnóstico preciso de casos e a detecção de infecções assintomáticas para determinar a extensão do surto de toxoplasmose.

Detection and treatment of acute toxoplasmosis during pregnancy can avoid severe disease of the fetus. In this context, assessment of anti-ToxoplasmaIgG avidity has been shown to exclude recent infection. The Elecsys Toxo IgG and IgM assays (Roche Diagnostics) have been validated for screening pregnant women and a new assay, Elecsys Toxo IgG Avidity, was recently developed. Our aims were to investigate the performance characteristics of this new avidity assay and explore whether additional information can be provided by avidity assays. The Elecsys assay was compared with the Vidas (bioMérieux) and Architect (Abbott) Avidity assays using two sets of serum samples (n= 291 andn= 255). The rate of general agreement between the Elecsys and Vidas assays was 74%, and that between the Elecsys and Architect assays was 83%. For 11% of the serum samples, avidity was high with the Vidas assay and within the gray zone with the Elecsys assay. None of the assays detected high-avidity antibodies in serum taken 90% were exclusively reported in sera taken >9 months after infection by the Elecsys and Architect assays. Almost all avidities of

Subramaniam Suresh1, Saidin Nor-Masniwati1, Muhd Nor Nor-Idahriani1, Wan-Hitam Wan-Hazabbah1, Mohamed Zeehaida2, Embong Zunaina11Department of Ophthalmology, 2Department of Medical Microbiology and Parasitology, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, MalaysiaBackground: The purpose of this study was to evaluate the immunoglobulin (Ig) G avidity of serological toxoplasmosis testing in patients with ocular inflammation and to determine the clinical manifestations of ocular toxoplasmosis.Methods: A retrospective review of all patients presenting with ocular inflammation to the Hospital Universiti Sains Malaysia, Kelantan, Malaysia between 2005 and 2009 was undertaken. Visual acuity, clinical manifestations at presentation, toxoplasmosis antibody testing, and treatment records were analyzed.Results: A total of 130 patients with ocular inflammation were reviewed retrospectively. The patients had a mean age of 38.41 (standard deviation 19.24, range 6–83) years. Seventy-one patients (54.6%) were found to be seropositive, of whom five (3.8%) were both IgG and IgM positive (suggestive of recently acquired ocular toxoplasmosis) while one (0.8%) showed IgG avidity ≤40% (suggestive of recently acquired ocular toxoplasmosis) and 65 patients (50.0%) showed IgG avidity >40% (suggestive of reactivation of toxoplasmosis infection). Chorioretinal scarring as an ocular manifestation was significantly more common in patients with seropositive toxoplasmosis (P = 0.036). Eighteen patients (13.8%) were diagnosed as having recent and/or active ocular toxoplasmosis based on clinical manifestations and serological testing.Conclusion: Ocular toxoplasmosis is a clinical diagnosis, but specific toxoplasmosis antibody testing helps to support the diagnosis and to differentiate between reactivation of infection and recently acquired ocular toxoplasmosis.Keywords: ocular toxoplasmosis, chorioretinal scar, toxoplasmosis antibody, IgG avidity test

Objective: To estimate the cost effectiveness ratio of performing serologic screening for toxoplasma in the first prenatal control and to continue or not with monthly or quarterly monitoring, to increase the diagnosed cases of pregnant women with Toxoplasma gondii infection with timely treatment.Methods: We built a decision tree in TreeAge® which considered four diagnostic strategies: i) No screening ii) IgG and IgM for toxoplasma in the first prenatal visit, and the performance of an IgG avidity test and repetition in two weeks according with the results; iii) IgG and IgM for toxoplasma in the first prenatal control, performance of IgG avidity test and repetition in two weeks according with the results, and quarterly monitoring with IgM and iv) IgG and IgM for toxoplasma in the first prenatal control, performance of IgG avidity test and repetition in two weeks according with the results, and monthly monitoring with IgM. The costs were included from the perspective of the Colombian health system and expressed in Colombian pesos of 2010. Medicines cost information was obtained from the 2008 SISMED (1) and the value of the diagnostic tests was calculated by adjusting the values of the Tariff Manual ISS 2001 30% (2), these values were compared with information of the costs supplied by three EPS. The discount rate was 0%. We performed sensitivity univariate and probabilistic analyses for costs and effectiveness.Results: The most effective and expensive strategy was found to be monthly monitoring, followed by quarterly monitoring, and no screening. Screening only in the first prenatal visit is a dominated strategy. The incremental cost-effectiveness ratio (ICER) of quarterly monitoring versus screening only in the first prenatal visit is $ 163,895,455; while the ICER of monthly versus quarterly monitoring is $ 418.906.009. According to the one-way sensitivity analysis, the variables that best explain the ICER variability are the incidence of congenital toxoplasmosis and the specificity of the IgM test. The probabilistic sensitivity analysis shows that, for a willingness to pay (WTP) below $175 million pesos it is more likely than not screening is a cost effective strategy. Between 175 million pesos and 407 million pesos, quarterly monitoring is more likely to be cost effective. For a WTP above $407 million pesos, the cost effective strategy is monthly monitoring.Conclusions: The cost-effective strategy for Colombia depends on the WTP per additional case of Toxoplasma gondii infection in pregnant women opportunely detected and treated. The WTP should take into account the cost for society of neurological damage or blindness cases due to the infection.

Serum samples, 100 in the total number, were collected from different laboratories in Tehran, Iran and tested for anti-Toxoplasma specific IgG and IgM antibodies using indirect immunofluorescent antibody test (IFAT). Using the IgG (chronic) and IgM (acute) positive samples, the IgG avidity test was performed by ELISA in duplicate rows of 96-well mi- crotiter plates. One row was washed with 6 M urea and the other with PBS (pH 7.2), then the avidity index (AI) was calcu- lated. Sixteen out of 18 (88.9%) sera with acute toxoplasmosis showed low avidity levels (AI≤ 50), and 76 out of 82 (92.7%) sera in chronic phase of infection showed high avidity index (AI> 60). Six sera had borderline ranges of AI. The results showed that the IgG avidity test by ELISA could distinguish the acute and chronic stages of toxoplasmosis in humans.

Retrospective evaluation of the kinetics of cytomegalovirus (CMV) seroconversion with CMV IgM, IgG, and IgG avidity assays, in a Swiss pregnant women population, has shown that the current published CMV serologic diagnostic algorithms were valid and fit for use. In 19% of the cases analyzed, CMV-specific IgM was detected before IgG.

There is a high degree of variability in the serologic response to Epstein-Barr virus (EBV) infection, especially in viral capsid antigen (VCA)-IgM antibodies. Therefore, additional tests are needed to confirm primary infection.We evaluated the value of IgG avidity determination in diagnosis of EBV infection in immunocompetent and immunocompromised patients.A total of 236 serum samples from immunocompetent patients with symptoms suggestive of EBV infection were tested for the presence of VCA-IgM/IgG antibodies and IgG avidity. Using IgG avidity, acute primary infection was confirmed in 56.7% of the immunocompetent patients with positive and in 1.8% of patients with negative VCA-IgM. Recent primary infection was documented in 8.9% of the IgM positive and 3.5% of the IgM negative patients. In patients with indeterminate serology (equivocal IgM), 6.7% were classified by avidity index (AI) as acute primary infection, 10.0% as post-acute and 83.3% as past infection cases.Concerning the 32 immunocompromised patients, recent primary infection was documented in 3 of the 14 IgM positive patients. High AI was detected in 11 of these patients, indicating an IgM response due to reactivation.Determination of IgG avidity in combination with classical serologic markers seems to be a reliable method to confirm primary infection both in immunocompetent and immunocompromised patients. It may be especially useful to differentiate cases of primary infection in patients with undetectable VCA-IgM antibodies or indeterminate routine EBV serology.

SummaryThe measurement of avidity (functional affinity) of specific IgG antibodies by recently developed simple techniques provides a sensitive and highly specific serodiagnosis for various infectious diseases. Obtained in a single serum sample, the IgG-avidity result may be used for rapid assessmen

An easy, rapid, and reproducible test to distinguish residual cytomegalovirus (CMV) immunoglobulin M (IgM) antibodies from antibodies produced in primary infection could be useful, especially for pregnant women. The CMV avidity of IgG antibodies with the VIDAS automated enzyme-linked fluorescent assay and 6 M urea was evaluated in a multicenter study to differentiate between primary CMV infections and past infections or reactivations. A total of 416 serum specimens were tested: 159 specimens were from follow-up of primary infections, and 257 were from past infections. All of the specimens from primary infections collected within 4 months (17 weeks) after the onset of the infection had an avidity index lower than 0.8. An avidity index higher than 0.8 excludes a recent primary infection of less than 4 months. However, an avidity index higher than 0.8 cannot confirm all past infections, since 48 specimens (18%) from past infections had an avidity index lower than 0.8 (between 0.5 and 0.8). The exclusion capacity could be improved (96.9%) by using a cutoff of 0.7, but this index would decrease the specificity of the technique, since the avidity index was found to be between 0.7 and 0.8 in two patients with recent primary infection. All specimens from primary infections obtained more than 4 months after the onset of infection had an avidity index more than 0.2. In this study, an avidity index less than 0.2 confirms the presence of a recent primary infection of less than 4 months. The VIDAS CMV IgG avidity test is a rapid, reproducible test with very good performance.

The measurement of the avidity of cytomegalovirus (CMV) immunoglobulin G (IgG) antibodies has been shown by several investigators to be useful in identifying and excluding primary CMV infections in pregnant women. In this work, we examined the diagnostic utility of reflex testing of CMV IgM-positive specimens from pregnant women by using a CMV IgG avidity assay. The utility of this approach was directly dependent on the sensitivity of the CMV IgM assay employed during the initial screen. The higher initial reactivity rate of the AxSYM CMV IgM assay was necessary in order to detect CMV IgM in specimens containing low-avidity CMV IgG antibodies, indicative of a primary CMV infection, which other CMV IgM assays (Behring, Vidas, Captia, and Eurogenetics) fail to detect in some cases. The use of the AxSYM CMV IgM assay, followed by an avidity test, should result in more accurate diagnosis of CMV infection in pregnant women.

Introducción: Toxoplasmosis (T) es una infección parasitaria crónica importante en pacientes inmunocompro-metidos y mujeres embarazadas. Es relevante discriminar entre fase aguda (TA) y fase crónica (TC). Su diagnóstico es serológico en inmunocompetentes (detección de IgG e IgM). Objetivo: Evaluar la utilidad del test de avidez IgG (A-IgG) para identificar la fase aguda y o crónica. Avidez es la fuerza de afinidad entre una inmunoglobulina específica y el epítope de la proteína antigénica del agente infectante, afinidad que aumenta con el tiempo. Pacientes y Métodos: Se usó un test cualitativo que mide la avidez de IgG, discriminando las dos fases. A 35 pacientes con diagnóstico clínico de TA y o TC, se les realizó IgG, IgM e A-IgG en Equipo VIDAS®. Resultados: Los pacientes con TA fueron positivos para IgM e IgG y presentaron avidez débil. Los 21 casos con TC 52% (n: 11) tuvieron IgM positivo y 100% (n: 21) tuvo IgG positiva con avidez fuerte. Discusión: Los resultados confirman que el test de A-IgG puede ser de gran utilidad en el diagnóstico de TA, concordancia: 100 % con test de referencia (IgM cualitativa + IgG cuantitativa). El resultado está disponible en menos de 24 hrs, pudiendo ser útil en el diagnóstico de TA en mujeres embarazadas. Introduction: Toxoplasmosis (T) is a major chronic parasitic infection in immunocompromised patients and pregnant women. It is important to discriminate between acute phase (AT) and chronic phase (CT). Diagnosis is serological in immunocompetent patients (concentration of IgG and IgM). Objective: To evaluate the utility of an IgG avidity test (A-IgG) to identify the acute and chronic stage. Avidity is the strength of affinity between a specific immunoglobulin and the protein antigenic epitope of the infecting agent, an affinity that increases over time. Patients and Methods: We used a qualitative kit that measures the avidity of IgG, discriminating the two phases. In 35 patients with clinical diagnosis of AT and/or CT, IgG, IgM and IgG A (VIDAS®) were performed. Results: Patients with AT were positive for IgM and IgG, but presented weak avidity. In the 21 cases with CT, 52% (n: 11) were IgM positive and 100% (n: 21) had positive IgG with strong avidity. Discussion: The results confirm that the test of A-IgG may be useful in the diagnosis of AT, and has 100% concordance with reference test (qualitative IgM + quantitative IgG). The result is available within 24 hrs, and may be useful in diagnosis of AT in pregnant women.

Background The interpretation of a positive IgM antibody result to human cytomegalovirus (HCMV) in a pregnant woman is of major importance for the correct management of the pregnancy. Determination of HCMV-specific IgG avidity is considered an useful approach for distinguishing IgM antibody due to primary HCMV infection from IgM antibody elicited during non-primary infection. Objective Comparative evaluation of eight commercial HCMV IgG avidity assays currently available in Europe. Study design A panel of 198 sequential samples collected from 65 pregnant women at 0–90, 91–180, and >180 days after the onset of primary HCMV infection was retrospectively tested by Abbott, BioMerieux, Bio-Rad, DiaSorin, Diesse, Euroimmun, Radim, and Technogenetics HCMV IgG avidity assays according to the manufacturer's instructions. Results None of the 198 samples tested yielded identical scores by the kits under evaluation. The Euroimmun and Radim assays showed the best correlation with expected results in terms of low (0–90 days), intermediate (90–180 days) and high (>180 days) avidity results, respectively. The best accuracy in diagnosing a recent ( 180 days after the onset) primary HCMV infection was shown by Radim followed by Euroimmun and Diesse. The best correlation with a well established in-house developed HCMV IgG avidity assay was shown by Radim. Conclusions HCMV IgG avidity kits need to be improved and standardized. In the meantime, highly specific IgM assays are preferable for screening purposes in pregnant women.

Background. The IgG avidity test is usually used for differentiating between primary and non-primary HCMV infection within 3 months. Weak avidity is highly suggestive of a primary infection, while high avidity tends to exclude it.An indeterminate or moderate avidity, however, does not allow a clear dating. Since there are several avidity tests with different performances, those tests that are able to minimize the results with indeterminate/moderate avidity are particularly useful. Objectives. The aim of our work was to evaluate the results obtained with two IgG avidity tests in IgG and IgM anti-HCMV positive patients. Study Design. 113 anti-HCMV IgG and IgM positive samples were tested with Enzime Linked Fluorescent Assay (ELFA) and Chemiluminescence Immuno Assay (CLIA) IgG avidity test. Results. 21 samples (18.6%), 50 (44.2%) and 42 (37.2%) with ELFA and 53 samples (46.9%), 10 (8.8%) and 50 (44.2%) with CLIA were found to have respectively low, indeterminate/moderate and high avidity. Of the 50 ELFA indeterminate avidity samples, 32 (64%), 10 (20%) and 8 (16%) were found to have respectively low, moderate and high CLIA.avidity. For 11 cases of the 32 ELFA indeterminate avidity and CLIA low avidity, there were previous data showing a seroconversion within three months. In a case of the 8 ELFA indeterminate avidity and CLIA high avidity, there were, instead, previous data of IgG and IgM positivity already four months earlier. Conclusions. It appears that the CLIA test for IgG avidity is more effective than ELFA for dating HCMV infection.

International audience; We assessed the performance of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays against corresponding assays on AxSYM and Vidas using 730 sera from pregnant women. The ARCHITECT Toxo IgG and IgM assays showed a relative sensitivity of 97.5% and 89.9% and a relative specificity of 99.1% and 99.8%, respectively. If IgM sensitivity is calculated only for sera drawn less than 4 months after infection, the relative sensitivity rises to 98.1%. Correlation between the ARCHITECT and Vidas Avidity assays was 0.87 (n = 103). Testing 86 IgG-positive specimens from recent infection (4 months) exhibited high avidity results in 72.5% (137/189) of cases. The method can be used reliably to exclude recent infections in sera with concurrently positive results for IgM and IgG (IgG, >3 IU/mL).

A novel methodology is introduced for rapid serological diagnosis. This methodology combines the antibody bridging assay principle with the measurement of antibody avidity. The combination allows the determination of the infection phase with a single dilution of a single sample of serum. This is a significant improvement on current serological techniques which often require either paired-sample testing (IgG/IgM serology) or testing of the sample in several dilutions (IgG avidity testing). Assay methods were developed on two immunoassay platforms; the heterogeneous time-resolved fluoroimmunoassay and the separation-free two-photon excitation fluorometry. The new methods were compared to conventional class-specific IgG/IgM and IgG avidity techniques. The major findings were that the avidity results of the new methodology were independent of the sample dilution (specific antibody concentration in serum) and consistent between immunoassay platforms. This new methodology is simple, rapid, and quick to perform. It provides the possibility of running serodiagnostic tests at point-of-care with bench-top random-access analyzers.

Laboratory diagnosis of toxoplasmosis is mainly based on serological methods, particularly important in the most challenging situations, as the diagnosis of primary infection during pregnancy and diagnosis of congenital infection. Tests for the detection of IgA antibodies are especially important in the newborns, because they are more sensitive than IgM conventional methods. The purpose of this study was to evaluate diagnostic performances of Enzygnost system for IgA detection, achieved by using Enzygnost Anti-human IgA/POD conjugate in combination with Enzygnost toxoplasmosis IgG (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). A retrospective study was performed with 591 serum samples submitted to the Microbiology Laboratory of S. Orsola Hospital in Bologna for toxoplasmosis screening.All the sera were tested by Enzygnost toxoplasmosis IgG, Enzygnost toxoplasmosis IgM and Enzygnost system for IgA (Siemens Healthcare Diagnostics). Border-Line or positive IgM results were confirmed by Vidas Toxo IgM (bioMerieux, Marcy l’Etoile, France). Finally, IgG Avidity was performed by Vidas Toxo IgG Avidity (bioMerieux) and LDBio Toxoplasma WB IgG/IgM (LDBio Diagnostics, Lyon, France). During the study period, 453 sera were IgA negative, 53 were Border-Line and 85 were positive when tested by Enzygnost system for IgA. No significative correlation was found between IgA positive results and low Avidity results.Three babies were correctly diagnosed as congenital toxoplasmosis infected infants because of the presence of IgA antibodies at birth. Enzygnost system for IgA anti-Toxoplasma showed good diagnostic performances.We conclude that the high sensitivity and specificity of and its suitability for automation make it an ideal screening test.

The aim of our study was to evaluate the automated enhanced-chemiluminescence VITROS EciQ (Ortho) system compared to the EIA ALISEI (Radim) system for the first level detection of CMV IgG and IgM antibodies. Samples derived from 95 immunocompetent patients were examined. Both systems showed similar results for CMV IgG: 63 samples were positive, 28 negative and 4 samples were weakly positive. The four weakly positive samples were subsequently confirmed with the LIAISON (DiaSorin) system. Agreement was 91% concerning CMV IgM detection: 79 samples were negative, 7 positive and 9 samples releved discrepancy between the two systems.When these 9 cases were tested with LIAISON system for CMV IgM and IgG and the CMV IgG avidity test, data revealed complete agreement between VITROS EciQ and LIAISON systems.VITROS EciQ system seems to be a valuable system for the first level diagnosis of CMV infection.

Toxoplasmosis acquired during pregnancy exposes the fetus to congenital toxoplasmosis. Avidity tests are commonly used to date time of infection to evaluate the fetal risk and to offer prenatal diagnosis. This study evaluated and compared 2 commercial avidity tests: Platelia™ Toxo IgG Avidity (Bio-Rad, Marnes la Coquette, France) and Liaison® Toxo IgG Avidity II (Diasorin, Saluggia, Italy) kits. In complement, a study of specific IgG and IgM in the 2 systems was carried out. Sensitivity and specificity of the avidity tests were 94.4% and 87.8% for the Liaison® and 91.3% and 98.5% for the Platelia™ methods, respectively. Percentages of complete discrepancies, partial discrepancies, and agreement between both tests were 1.1%, 23.6%, and 75.3%, respectively. Moreover, the combination of both avidity tests may be useful in some cases. Indeed, that strategy permitted to confirm without delay a chronic toxoplasmosis in 23 cases and avoid treatment in these pregnant women.

SUMMARY Human toxocariasis is a zoonosis caused by infection with larvae of the ascarid nematode Toxocara canis and, less frequently, T. cati. Our study developed a method for distinguishing distant from recent human toxocariasis by assessing the avidity of the IgG antibodies. The avidity of specific antibodies increases with time after antigen challenge and assessment of the degree of avidity can be used to discriminate between recent and distant infections. The relative avidity was measured in 150 sera from children with visceral toxocariasis and in 46 sera from children with ocular toxocariasis. The probable time of infection was estimated on the basis of the medical history and clinical syndrome. Our study showed that 94·2% of positive sera collected from patients reporting infection > 6 months ago had high IgG avidity values, confirming distant toxocariasis, whereas 25·9% of positive sera taken

The seroprevalence of toxoplasmosis in 832 pregnant women in Miracema, Rio de Janeiro, was determined and 75.1% (625) and 2.0% (17) were anti-Toxoplasma gondii IgG and IgM positive, respectively. Out of the 17 IgM positive pregnant women, only one had low avidity IgG corresponding to the acute phase of the infection. All the other women presented with high avidity IgG and also presented with residual IgM anti-T. gondii. Of this sample, 106 received home visits (this includes 11 family nuclei of pregnant women with residual IgM anti-T. gondii, 68 nuclei of only IgG positive pregnant women and 27 nuclei of pregnant women with no antibodies to anti-T. gondii), resulting in 267 individuals visited. Out of these 267 individuals, 21 were positive for IgG and IgM anti-T. gondii and were candidates for the IgG avidity test. All of them presented with high avidity IgG and residual IgM. Five of these IgM+ individuals were (5/238; 2.1%) relatives of IgM negative pregnant women. The other 16 (16/29; 55.2%) were relatives of IgM+ pregnant women who were positive for residual IgM anti-T. gondii. This association was statistically significant (p = 0.0000). The analysis presented herein raises questions regarding the presence of residual IgM anti-T. gondii such as genetic determinants or even constant antigenic stimuli for the same family cluster.

Aim: To asses the value of IgG avidity in diagnosis of CMV infection in pregnant women and newborn infants. Methods: During the three-year period (2003-2005) serum samples from 64 pregnant women and 32 infants less than 12 months of age with suspected congenital/perinatal CMV infection were collected. Sera were tested for CMV IgM and IgG using an indirect enzyme-linked immunosorbent assay and IgG avidity using urea as denaturing agent. Results: Among IgM positive women, 2/26 (7.6%) showed an increase of IgG avidity index (AI) from intermediate to high AI in paired sera samples indicating recent primary infection and 24/26 (92.4%) showed high AI indicating past infection. All women with negative IgM antibodies had high AI. In infants less than 12 months old, acute/recent primary CMV infection was documented in 8/12 (66.7%) children with positive IgM and in 10/20 (50.0%) children with negative IgM antibodies. In two children less than three months with high AI, CMV infection was confirmed by virus isolation from urine. One of them showed a decrease of AI from high to low in paired sera samples. Conclusions: IgG avidity differentiates primary from nonprimary CMV infection in both pregnant women and infants older than three months. In children less than 3 months of age, transplacentally transferred maternal antibodies of high avidity may influence on the serologic test results., Cilj rada: Ispitati vrijednost IgG aviditeta u dijagnostici CMV infekcije u trudnica i novorodencadi. Metode: Tijekom trogodišnjeg perioda (2003-2005) prikupljeni su uzorci seruma od 64 trudnice, te 32 djece do godinu dana starosti sa suspektnom kongenitalnom/perinatalnom CMV infekcijom. Serumi su testirani na prisustvo CMV IgM i IgG protutijela metodom ELISA, te aviditet IgG protutijela uz primjenu uree. Rezultati: U skupini trudnica s pozitivnim IgM protutijelima, u njih 2/26 (7,6%) dokazan je porast indeksa IgG aviditeta (AI), od granicnog u visoki AI u parnim uzorcima seruma, što ukazuje na nedavnu primarnu CMV infekciju, dok je 24/26 (92,4%) imalo visok AI (prošla CMV infekcija). Sve trudnice s negativnim IgM protutijelima imale su visok AI. U djece mlade od 12 mjeseci, akutna/nedavna primarna CMV infekcija dokazana je u 8/12 (66,7%) djece s pozitivnim IgM, te u 10/20 (50,0%) djece s negativnim IgM protutijelima. U dvoje djece mlade od 3 mjeseca s visokim AI, CMV infekcija je potvrdena izolacijom virusa iz urina. U jednog od njih došlo je do pada AI iz visokog u niski, u parnom uzorku seruma. Zakljucci: Pomocu testa IgG aviditeta moguce je razluciti primarnu od prošle CMV infekcije u trudnica i djece starije od 3 mjeseca. U djece mlade od 3 mjeseca, transplacentarno prenesena majcina IgG protutijela visokog aviditeta mogu utjecati na rezultate seroloških pretraga.

Aim: To asses the value of IgG avidity in diagnosis of CMV infection in pregnant women and newborn infants. Methods: During the three-year period (2003-2005) serum samples from 64 pregnant women and 32 infants less than 12 months of age with suspected congenital/perinatal CMV infection were collected. Sera were tested for CMV IgM and IgG using an indirect enzyme-linked immunosorbent assay and IgG avidity using urea as denaturing agent. Results: Among IgM positive women, 2/26 (7.6%) showed an increase of IgG avidity index (AI) from intermediate to high AI in paired sera samples indicating recent primary infection and 24/26 (92.4%) showed high AI indicating past infection. All women with negative IgM antibodies had high AI. In infants less than 12 months of age, acute/recent primary CMV infection was documented in 8/12 (66.7%) children with positive IgM and in 10/20 (50.0%) children with negative IgM antibodies. In two children less than three months with high AI, CMV infection was confirmed by virus isolation from urine. One of them showed a decrease of AI from high to low in paired sera samples. Conclusions: IgG avidity differentiates primary from nonprimary CMV infection in both pregnant women and infants older than three months. In children less than 3 months of age, transplacentally transferred maternal antibodies of high avidity may influence on the serologic test results.

A comparative evaluation of 384 selected sera was performed using the Beckman Coulter Access and Abbott Axsym Toxo-IgG assays. The Axsym assay yields positive early results following infection, while the Access assay gives higher titres during chronic infection. The ratio between the two complementary tests, Axsym Toxo-IgG/Access Toxo-IgG (Ax/Ac), was compared with the Vidas anti-Toxoplasma IgG avidity index (AI). The Ax/Ac ratio decreased progressively as the time between infection and sampling increased. The mean Ax/Ac values (+/-SE) were 2.50 (+/-0.26), 2.14 (+/-0.13), 2.33 (+/-0.22), 1.34 (+/-0.09), 1.32 (+/-0.10), 0.92 (+/-0.08) and 0.74 (+/-0.07) for groups of sera sampled at 1, 2, 3, 4-5, 6-8, 9-12 and 13-24 months, respectively, after infection in pregnant women. These values were much smaller for cases with chronic infection (24 months), i.e., 0.56 (+/-0.03), 0.44 (+/-0.04) and 0.53 (+/-0.04), respectively, for pregnant women and immunodepressed patients with and without reactivation. Taking a ratio of 1 as a threshold for recent infection, the patients in the groups sampled at 1, 2 and 3 months had Ax/Ac ratios1 in 49/50 (98%), 53/55 (96.4%) and 36/36 (100%) cases, respectively. Thus, an Ax/Ac ratio of1 in serum from a pregnant woman allows a recent infection (3 months) to be excluded. This technique has the advantage of yielding positive results that develop much more rapidly than the AI, thereby helping to reassure large numbers of pregnant women and avoiding costly and unnecessary prophylactic treatment and follow-up.

AcuteToxoplasma gondiiinfection in early pregnancy carries the risk of transmitting the infection to the fetus with serious sequelae. However, serological testing for IgG/IgM anti-Toxoplasmaantibodies may fail to differentiate between a recent and past infection. Two hundred and twenty-four Kuwaiti women in their first trimester were screened for IgG/IgM antibodies by the Vitek Immuno Diagnostic Assay System (VIDAS) and VIDAS IgG-avidity tests. On serological screening, 119 (53.1 %) women were positive for IgG antibodies and 31 (13.8 %) for IgM antibodies. Nine of the IgM-positive and 7 IgM-negative women had low-avidity antibodies. However, the IgG-avidity test detected low-avidity antibodies only in 9 (29 %) of the 31 IgM-positive women, suggesting a recent infection; 19 (61.3 %) women had high-avidity antibodies, indicating that the infection was acquired in the distant past. Based on IgM serology alone, at least 31 IgM-positive women may have been wrongly labelled as having acuteToxoplasmainfection thus warranting appropriate therapeutic intervention. All the 19 IgM-positive women with high-avidity antibodies were confirmed negative forToxoplasmaDNA on PCR analysis. Compared with PCR analysis, the VIDAS avidity test was a helpful tool for the diagnosis of recentToxoplasmainfection in IgM-negative women with low-avidity antibodies and IgM-positive women with high-avidity antibodies; the specificity was >85 –100 %. It is concluded that the VIDAS avidity test when used in combination with VIDAS IgG/IgM tests is a valuable assay for the exclusion of ongoing or recently acquiredT. gondiiinfection in pregnant women in their first trimester and that it decreases significantly the necessity for follow-up testing and unnecessary therapeutic intervention.

We measured rubella virus immunoglobulin G (IgG) and IgM levels, as well as IgG avidity indexes, in serum samples taken before or after 6 months either after infection or after vaccination. The results obtained indicate that humoral immune responses are different after primary infection and after vaccination. This may have important consequences on the serological diagnosis of rubella virus infection.

From March to April 2006, an outbreak of mumps occurred in Gyeonggi, Korea. The aim of this study was to describe and discriminate between primary and secondary vaccine failure in a highly vaccinated population for mumps using IgG avidity testing. Fifteen clinical mumps cases occurred among 41 students. Among these 15 patients, 11 vaccinated patients were considered secondary vaccine failures with high IgG titers and a high avidity index (AI,or =32%); an unvaccinated patient was considered to have primary infection with high IgG titers and low AI, and three vaccinated patients were considered as other infections with low IgG titers and low AI. Among 26 unaffected students, 5 vaccinated patients were retrospectively diagnosed as sub-clinical infection with high IgG titers and high AI; the remaining students had low IgG titers and low AI except for one previously infected student. The results of this study show that secondary vaccine failure played an important role in this mumps outbreak. Therefore, booster immunization for mumps should be considered in immunized adolescents to prevent further outbreaks.

Min (AU/mL) Max (AU/mL) 25 97 22 65.9 6 60.3 5 50 5 50 5 47 The CMV LIAISON® XL CLIA-IgM assay showed a very good specificity in samples from active and no active CMV infection compared to that one found with Architect CMIA-IgM assay (98.4% versus 12.7%). We observed a very good agreement between the results obtained from CLIA-IgM and IB-IgM tests. Among the 63 serum samples from cord blood donors, 62 were positive or negative with both assays whereas the CMIAIgM test was in agreement with IB-IgM test in only 8 of the 63 samples. In pregnancy, the most important requirement for a CMV IgG avidity assay is to help in identifying or excluding a primary infection occurring in the previous 3 months in women presenting with a positive CMV IgM result. The 98% of samples taken 180 days after infection onset were reported as high-avidity CMV IgG by the LIAISON® XL CMV IgG Avidity assay. Between 90 and 120 days after infection onset the percentage of samples with low-moderate IgG avidity was still very high (76.5%). A mixture of low-moderate avidity and high-avidity were observed in samples taken 120–180 days after infection onset. The latter observation is consistent with the fact that the kinetics of the IgG avidity maturation process is likely to vary between individuals. Therefore, the LIAISON® XL system appears useful for accurately diagnosing of CMV infection in pregnant women. CONCLUSION

Anti-Toxoplasma IgG-avidity was determined in 168 serum samples from IgG- and IgM-positive pregnant women at various times during pregnancy, in order to evaluate the predictive value for risk of mother-to-child transmission in a single sample, taking the limitations of conventional serology into account. The neonatal IgM was considered the serologic marker of transmission. Fluorometric tests for IgG, IgM (immunocapture) and IgG-avidity were performed. Fifty-one of the 128 pregnant women tested gave birth in the hospital and neonatal IgM was obtained. The results showed 32 (62.75%) pregnant women having high avidity, IgM indexes between 0.6 and 2.4, and no infected newborn. Nineteen (37.25%) had low or inconclusive avidity, IgM indexes between 0.6 and 11.9, and five infected newborns and one stillbirth. In two infected newborns and the stillbirth maternal IgM indexes were low and in one infected newborn the only maternal parameter that suggested fetal risk was IgG-avidity. In the present study, IgG-avidity performed in single samples from positive IgM pregnant women helped to determine the risk of transmission at any time during pregnancy, especially when the indexes of the two tests were analysed with respect to gestational age. This model may be less expensive in developing countries where there is a high prevalence of infection than the follow-up of susceptible mothers until childbirth with monthly serology, and it creates a new perspective for the diagnosis of congenital toxoplasmosis. A avidez de IgG anti-Toxoplasma foi realizada em 168 amostras IgG e IgM positivas de gestantes, coletadas em qualquer período da gestação, para avaliar o valor preditivo do risco de transmissão materno-fetal em amostra única, considerando as limitações da sorologia convencional. A IgM neonatal foi considerada o marcador sorológico de transmissão. Testes fluorométricos foram realizados para IgG, IgM (imunocaptura) e avidez de IgG. Cinqüenta e uma das 128 gestantes testadas tiveram os partos realizados na instituição e a IgM neonatal foi obtida. Os resultados mostraram 32 (62.75%) gestantes com avidez alta, índices de IgM entre 0,6 e 2,4 e nenhum recém-nascido infectado. Dezenove (37.25%) tiveram avidez baixa ou inconclusiva, índices de IgM entre 0,6 e 11,9, cinco recém-nascidos infectados e um natimorto. Em dois recém-nascidos infectados e no natimorto, os índices maternos de IgM foram baixos e em um recém-nascido infectado, o único parâmetro materno que sugeriu risco para o feto foi a avidez de IgG. No presente estudo, a avidez de IgG realizada em amostras isoladas de gestantes IgM positivas auxiliou a determinar o risco de transmissão durante toda a gestação, especialmente quando os índices dos dois testes foram analisados em relação à idade gestacional. Este modelo pode ser menos oneroso para países em desenvolvimento com alta prevalência da infecção e cria nova perspectiva para o diagnóstico da toxoplasmose congênita.

OBJETIVO: descrever e analisar os resultados da sorologia convencional para toxoplasmose em gestantes acompanhadas pelo pré-natal do Hospital Materno-Infantil Presidente Vargas em Porto Alegre. MÉTODOS: IgG e IgM específicas foram processadas por testes fluorométricos, sendo a IgM de captura. Nova coleta em duas a três semanas foi solicitada às gestantes IgM positivas e as que estavam no início da gestação tiveram realizada a avidez de IgG. IgM neonatal foi obtida nos partos realizados na instituição. A análise foi baseada na distribuição binomial, por meio do cálculo de uma proporção simples para estimar a prevalência de soropositividade e suscetibilidade à infecção pelo Toxoplasma gondii. RESULTADOS: a prevalência da infecção em 10.468 gestantes foi de 61,1 e 38,7% das gestantes eram suscetíveis. Entre as 272 gestantes IgG e IgM positivas, 87 retornaram para nova coleta e em 84 os níveis de anticorpos permaneceram inalterados. De nove gestantes com avidez, houve apenas uma gestante com avidez baixa e a IgM neonatal do recém-nascido foi positiva. Em 44 recém-nascidos na instituição, a IgM neonatal foi positiva em quatro. CONCLUSÕES: encontrou-se alta prevalência da infecção em gestantes e de toxoplasmose congênita, mesmo sem dados sobre soroconversão. A maioria das sorologias IgM positivas foi relacionada a infecção passada. A relação custo-benefício do pré-natal em amostras isoladas pode ser otimizada com a análise do risco de transmissão materno-fetal nas gestantes IgM positivas. Quando houver risco, deve-se solicitar teste de IgM do recém-nascido e acompanhá-lo durante o primeiro ano de vida. PURPOSE: to describe and analyze the results of conventional serology for toxoplasmosis in pregnant women during prenatal care at the Hospital Materno-Infantil Presidente Vargas in Porto Alegre. METHODS: specific IgG and IgM determinations were performed using fluorometric tests, with IgM capture. A second sample within two to three weeks was requested from all IgM-positive pregnant women and IgG avidity was performed in IgM-positive pregnant women at the beginning of pregnancy. Neonatal IgM was obtained when the delivery occurred at the institution. The analysis was based on the binomial distribution, through simple ratio estimate, to assess soropositivity prevalence and susceptibility to T. gondi infection. RESULTS: the prevalence of infection in 10,468 pregnant women was 61.1% and 38.7% pregnant women were susceptible. Among the 272 IgG and IgM-positive pregnant women, 87 returned for a second test and in 84 of them the antibody levels remained unchanged. Of nine pregnant women with avidity, there was only one low avidity and her newborn was IgM positive. In 44 newborns delivered at the institution, the neonatal IgM was positive in four. CONCLUSIONS: a high prevalence of infection and congenital toxoplasmosis was found in pregnant women, even without data on seroconversion. Most of the IgM-positive serologies were related to past infection. The cost-benefit ratio of prenatal care in isolated samples may be optimized analyzing the risk of mother-to-child transmission in IgM-positive pregnant women. When there is a risk, a neonatal IgM test must be requested and the newborn should be followed during the first year of life.

In 1983 the Osterreichische Gesellschaft für Qualitätssicherung und Standardisierung medizinisch-diagnostischer Untersuchungen (OQUASTA) has invited the Department of Medical Parasitology of the Clinical Institute of Hygiene and Medical Microbiology, University of Vienna (today: Medical University of Vienna), to establish an external quality assessment service on the detection of specific antibodies against Toxoplasma gondii, one of the most prevalent protozoic parasites in the world. The objective of this project was the support of Austrian laboratories in standardising their test methods for the detection of specific antibodies against T. gondii. Between 1983 and 2004, 45 collaborating studies were carried out. During this period, the number of participating laboratories has increased from 10 in 1983 to about 50 in recent years. In total, the test results produced by the laboratories matched with the nominal values in more than 90%. On the examples of three human cases we demonstrate that externally validated serological methods alone, despite their great benefit, are not enough for a sufficient serodiagnosis of toxoplasmosis; unusually complicated serological situations do arise and can only be met by the knowledge about special tests, the application of an appropriate examination strategy and -- last but not least -- by many years of experience.

The aim of this study was the comparison of a fully automated random access system IMMULITE 2000 (DPC) with a semiautomated system VIDAS (bioMerieux) for the first level detection of Toxoplasma-specific IgG and IgM antibodies. In total, 295 samples were examined for Toxoplasma- specific IgG.The comparison between the VIDAS IgG assay and IMMULITE IgG assay showed the same result for 290 samples (98.3%). Particularly, 220 samples were negative, 70 positive and 4 samples were positive with IMMULITE and equivocal with VIDAS. Only one sample showed a discrepant result: positive with IMMULITE and negative with VIDAS. A total of 124 samples were tested for Toxoplasma-specific IgM and 33 were positive or equivocal with VIDAS IgM assay and 30 of these were also tested for Toxoplasma-specific IgG avidity. The comparison between the VIDAS IgM assay and IMMULITE IgM assay showed the following results: 23 samples were positive in the two systems, 4 samples were equivocal with the VIDAS IgM assay but positive in IMMULITE IgM assay, 6 samples were positive or equivocal in the VIDAS IgM assay but negative in IMMULITE IgM assay.The study of the 6 discrepant samples showed: 2 samples with the presence of natural IgM, 3 samples with a high IgG avidity index and 1 with an intermediate IgG avidity index. IgM was not detected with both assays in any of the other samples.The IMMULITE system seems to be a valuable system for the first level diagnosis of Toxoplasma infection.

We have developed a cheaper an simple in house indirect ELISA that uses the live attenuated VZV vaccine as a coating antigen. The alternative ELISA had an agreement of 94% when compared with a commercial VZV ELISA kit. Moreover, our ELISA proved to be more reliable than the kit when assessing true negative samples. By adding a standard serum, we were able to produce results in international units per millilitre. Also, the addition of an extra step with 8M urea allowed the assessment of VZV IgG avidity without excessive costs. The cost per sample to test VZV IgG was 2.7 times cheaper with our ELISA, allowing the testing of many samples without the burden of production of VZV antigen in the laboratory.

The nearly 40-year long debate on the relevance of secondary measles vaccination failure has been inconclusive because a feasible method for the assessment of the duration of immunity has been lacking. Even if a two-dose measles vaccination policy is now universally endorsed, WHO still officially adheres to the view that a single successful measles vaccination, without natural boosters, induces a lifelong immunity and deems secondary failures epidemiologically irrelevant - in the belief that the latter are rare and do not participate in the transmission chain. A recently published study on measles-IgG avidity, which allows for separation of secondary from primary vaccination failures, tentatively showed that the official view does not necessarily hold true. The results may have wide implications on global measles eradication efforts. The potential of IgG avidity measurement in complex postvaccination measles epidemiology is discussed.

Background IgG anti- Toxoplasma avidity tests have proven useful to discriminate between recent and distant infection in management of pregnant women with anti- Toxoplasma -IgM antibodies. This study was performed to compare two commercially available IgG anti- Toxoplasma avidity test kits. Methods Sixty-four samples positive for IgM and IgG anti- Toxoplasma antibodies were analyzed with two IgG anti- Toxoplasma avidity tests: VIDAS Toxo IgG avidity kit (BioMerieux, Marcy-l'Etoile, France) and Toxoplasma gondii IgG avidity EIA kit (Labsystems, Helsinki, Finland). Samples were obtained from both pregnant women and subjects in different clinical settings. Results Of 64 sera positive in both VIDAS Toxo IgG and VIDAS Toxo IgM tests, 19 (29.7%) had high avidity antibodies in VIDAS and 17 (26.6%), high avidity antibodies in Labsystems kit. A total of 48 (75.0%) of 64 sera showed concordant results between VIDAS and Labsystems Toxo IgG avidity tests; one (1.2%) serum sample showed discordant results and in 15 (23.4%) sera, results were high or low in one test and borderline in the other. Overall correlation coefficient for results obtained in both tests was 0.80 (0.60 in sera of pregnant women and 0.88 in sera of other patients, respectively). Conclusions Correlation between results obtained in BioMerieux and Labsystems Toxo IgG avidity kits in sera from pregnant women as well other individuals was high. BioMerieux assay possesses the advantage of automatization but requires the VIDAS machine; in contrast, Labsystems assay is less costly but requires time-intensive manual performance and calculation of test results.

Classical serologic assays are not useful for the diagnosis of perinatal herpes simplex virus (HSV) infection during the acute phase of the disease. We report two cases of neonatal HSV infection that highlight the diagnostic value of HSV-specific IgG avidity and its contribution for further characterization of neonatal HSV infection.

Measurement of cytomegalovirus (CMV)-specific immunoglobulin G (IgG) avidity has proven to be a powerful tool for distinguishing primary from nonprimary CMV infection. An in-house enzyme-linked immunosorbent assay (ELISA) for measuring CMV IgG avidity was validated using 84 sera from pregnant women who had recently seroconverted following primary CMV infection and 74 sera from individuals with past CMV infection (IgG-positive and IgM-negative profile). Of the 84 sera from pregnant women, 73 sera were collected within 120 days of the last IgG-negative sample, and 72 of these 73 sera (99%) exhibited an avidity index (AI) of 60%. Thus, low avidity in the in-house ELISA was defined as an AI of ⩽50%, whereas high avidity was defined as an AI of ⩾60%. In additional studies, the relationship between CMV IgG avidity and CMV IgM levels was examined using 64 CMV IgG-positive sera (time since seroconversion unknown) exhibiting equivocal or positive results in a CMV IgM capture ELISA (Diamedix). Of these 64 sera, 29 exhibited IgM index values of ⩾3.0, and 27 of these 29 (93%) exhibited low IgG avidity. A similar trend was observed when a subset of these 64 sera ( n = 48) was tested in another CMV IgM capture ELISA (Trinity); of 18 sera with IgM index values of ⩾3.0, 17 (94%) exhibited low IgG avidity. These findings demonstrate the validity of an in-house ELISA for CMV IgG avidity and further show that strong reactivity of CMV IgG-positive sera in either of two CMV IgM capture assays is a reliable indicator of low CMV IgG avidity, and thus, recent CMV infection.