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Using paired serum samples obtained from patients with illness associated with increases in anti-human coronavirus OC43 (HCoV-OC43) or anti-HCoV-229E antibodies, we examined the possibility of false-positive results detected in a recombinant severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV) nucleocapsid protein immunoglobulin G enzyme-linked immunosorbent assay (ELISA). Three of the 21 and 1 of the 7 convalescent-phase serum samples from persons with increases in antibodies against HCoV-OC43 and HCoV-229E, respectively, tested positive by the recombinant SARS-CoV nucleocapsid protein-based ELISA. None of these samples were found to contain a specific antibody in the recombinant SARS-CoV spike polypeptide-based Western blot assay.

As the COVID-19 pandemic progresses, there is an increasing need for rapid, accessible assays for SARS-CoV-2 detection. We present a clinical evaluation and real-world implementation of the INDICAID COVID-19 rapid antigen test (INDICAID rapid test). A multisite clinical evaluation of the INDICAID rapid test using prospectively collected nasal (bilateral anterior) swab samples from symptomatic subjects was performed. The INDICAID rapid test demonstrated a positive percent agreement (PPA) and negative percent agreement (NPA) of 85.3% (95% confidence interval [95% CI], 75.6% to 91.6%) and 94.9% (95% CI, 91.6% to 96.9%), respectively, compared to laboratory-based reverse transcriptase PCR (RT-PCR) using nasal specimens. The INDICAID rapid test was then implemented at COVID-19 outbreak screening centers in Hong Kong as part of a testing algorithm (termed “dual-track”) to screen asymptomatic individuals for prioritization for confirmatory RT-PCR testing. In one approach, preliminary positive INDICAID rapid test results triggered expedited processing for laboratory-based RT-PCR, reducing the average time to confirmatory result from 10.85 h to 7.0 h. In a second approach, preliminary positive results triggered subsequent testing with an onsite rapid RT-PCR, reducing the average time to confirmatory result to 0.84 h. In 22,994 asymptomatic patients, the INDICAID rapid test demonstrated a PPA of 84.2% (95% CI, 69.6% to 92.6%) and an NPA of 99.9% (95% CI, 99.9% to 100%) compared to laboratory-based RT-PCR using combined nasal/oropharyngeal specimens. The INDICAID rapid test has excellent performance compared to laboratory-based RT-PCR testing and, when used in tandem with RT-PCR, reduces the time to confirmatory positive result. IMPORTANCE Laboratory-based RT-PCR, the current gold standard for COVID-19 testing, can require a turnaround time of 24 to 48 h from sample collection to result. The delayed time to result limits the effectiveness of centralized RT-PCR testing to reduce transmission and stem potential outbreaks. To address this, we conducted a thorough evaluation of the INDICAID COVID-19 rapid antigen test, a 20-minute rapid antigen test, in both symptomatic and asymptomatic populations. The INDICAID rapid test demonstrated high sensitivity and specificity with RT-PCR as the comparator method. A dual-track testing algorithm was also evaluated utilizing the INDICAID rapid test to screen for preliminary positive patients, whose samples were then prioritized for RT-PCR testing. The dual-track method demonstrated significant improvements in expediting the reporting of positive RT-PCR test results compared to standard RT-PCR testing without prioritization, offering an improved strategy for community testing and controlling SARS-CoV-2 outbreaks.

Streptococcus pneumoniae (the pneumococcus) is a significant global pathogen. Accurate identification and serotyping are vital. In contrast with World Health Organization recommendations based on culture methods, we demonstrate that pneumococcal identification and serotyping with molecular methods are affected by sample type. Results from oropharyngeal samples from adults were often inaccurate. This is particularly important for assessment of vaccine impact using carriage studies, particularly in low- and middle-income countries where there are significant barriers for disease surveillance., Streptococcus pneumoniae (the pneumococcus) carriage is commonly used to measure effects of pneumococcal vaccines. Based on findings from culture-based studies, the World Health Organization recommends both nasopharyngeal (NP) and oropharyngeal (OP) sampling for detecting adult carriage. Given evidence of potential confounding by other streptococci, we evaluated molecular methods for pneumococcal identification and serotyping from 250 OP samples collected from adults in Fiji, using paired NP samples for comparison. Samples were screened using lytA quantitative PCR (qPCR), as well as pneumococcal identification and serotyping conducted by DNA microarray. A subset of OP samples were characterized by latex sweep agglutination and multiplex PCR. Alternate qPCR assays (piaB and bguR) for pneumococcal identification were evaluated. The lytA qPCR was less specific and had poor positive predictive value (PPV) in OP samples (88% and 26%, respectively) compared with NP samples (95% and 64%, respectively). Using additional targets piaB and/or bguR improved qPCR specificity in OP, although the PPV (42 to 53%) was still poor. Using microarray, we found that 102/107 (95%) of OP samples contained nonpneumococcal streptococci with partial or divergent complements of pneumococcal capsule genes. We explored 91 colonies isolated from 11 OP samples using various techniques, including multiplex PCR, latex agglutination, and microarray. We found that nonpneumococcal streptococci contribute to false positives in pneumococcal serotyping and may also contribute to spurious identification by qPCR. Our results highlight that molecular approaches should include multiple loci to minimize false-positive results when testing OP samples. Regardless of method, pneumococcal identification and serotyping results from OP samples should be interpreted with caution. IMPORTANCE Streptococcus pneumoniae (the pneumococcus) is a significant global pathogen. Accurate identification and serotyping are vital. In contrast with World Health Organization recommendations based on culture methods, we demonstrate that pneumococcal identification and serotyping with molecular methods are affected by sample type. Results from oropharyngeal samples from adults were often inaccurate. This is particularly important for assessment of vaccine impact using carriage studies, particularly in low- and middle-income countries where there are significant barriers for disease surveillance.

We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients., We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients. The interference factors causing false-positive reactivity with the two methods were analyzed, and the urea dissociation test was employed to dissociate the SARS-CoV-2 IgM-positive serum using the best dissociation concentration. The two methods detected positive SARS-CoV-2 IgM in 22 mid-to-high-level-RF-IgM-positive sera and 14 sera from COVID-19 patients; the other 50 sera were negative. At a urea dissociation concentration of 6 mol/liter, SARS-CoV-2 IgM results were positive in 1 mid-to-high-level-RF-IgM-positive serum and in 14 COVID-19 patient sera detected using GICA. At a urea dissociation concentration of 4 mol/liter and with affinity index (AI) levels lower than 0.371 set to negative, SARS-CoV-2 IgM results were positive in 3 mid-to-high-level-RF-IgM-positive sera and in 14 COVID-19 patient sera detected using ELISA. The presence of RF-IgM at mid-to-high levels could lead to false-positive reactivity of SARS-CoV-2 IgM detected using GICA and ELISA, and urea dissociation tests would be helpful in reducing SARS-CoV-2 IgM false-positive results.

A previously healthy 43-year-old female presented to her primary care physician with a 13-day history of recurrent nightly fevers (100°F to 101°F), nonproductive cough, and respiratory congestion. She was prescribed azithromycin, albuterol, and benzonatate. She presented to the emergency center 2

OXA-181 is the second most common global OXA-48-like carbapenemase and is endemic in the Indian subcontinent. Molecular studies have shown that Enterobacterales with OXA-181 are often introduced into regions of nonendemicity. Distinguishing OXA-181 from other OXA-48-like enzymes often requires sequencing, which is rather expensive and time-consuming. A specific PCR (i.e., OXA181PCR) for the detection of blaOXA-181 was validated using a global collection (n = 315) of bacteria with well-characterized carbapenemases and showed 100% sensitivity and specificity (95% confidence interval [CI], 94.1 to 100 and 98.6 to 100, respectively) for detecting bacteria with OXA-181. The OXA181PCR subsequently gave positive results on 58/160 (36%) Enterobacterales with OXA-48-like carbapenemases from the 2015 INFORM surveillance program. The blaOXA-181-positive Enterobacterales were present in 9 countries spanning 5 continents, illustrating the global distribution of OXA-181. This methodology can easily be incorporated into molecular surveillance programs to provide accurate information about the prevalence of OXA-181. A loop-mediated isothermal amplification (LAMP)-OXA48 assay overall performed well for detecting OXA-48-like enzymes but showed poor specificity due to false-positive results with non-OXA carbapenemases.

Current measures to prevent TGEV from entering a naive herd include quarantine and testing for TGEV-seronegative animals. However, TGEV serology is complicated due to the cross-reactivity with PRCV, which circulates subclinically in most swine herds worldwide. Conventional serological tests cannot distinguish between TGEV and PRCV antibodies; however, blocking ELISAs using antigen containing a large deletion in the amino terminus of the PRCV S protein permit differentiation of PRCV and TGEV antibodies. Several commercial TGEV/PRCV blocking ELISAs are available, but performance comparisons have not been reported in recent research. This study demonstrates that the serologic cross-reactivity between TGEV and PRCV affects the accuracy of commercial blocking ELISAs. Individual test results must be interpreted with caution, particularly in the event of suspect results. Therefore, commercial TGEV/PRCV blocking ELISAs should only be applied on a herd basis., This study compared the performances of three commercial transmissible gastroenteritis virus/porcine respiratory coronavirus (TGEV/PRCV) blocking enzyme-linked immunosorbent assays (ELISAs) using serum samples (n = 528) collected over a 49-day observation period from pigs inoculated with TGEV strain Purdue (n = 12), TGEV strain Miller (n = 12), PRCV (n = 12), or with virus-free culture medium (n = 12). ELISA results were evaluated both with “suspect” results interpreted as positive and then as negative. All commercial kits showed excellent diagnostic specificity (99 to 100%) when testing samples from pigs inoculated with virus-free culture medium. However, analyses revealed differences between the kits in diagnostic sensitivity (percent TGEV- or PRCV-seropositive pigs), and all kits showed significant (P

Here, we report a significant increase in positivity rate among low-risk health care workers (HCW) undergoing annual tuberculosis (TB) testing in our health system after the fourth-generation QuantiFERON-TB Gold Plus (QFT-Plus) assay replaced the QuantiFERON-TB Gold (QFT) assay. Compared to its

The Epistem Genedrive assay rapidly detects the Mycobacterium tuberculosis complex from sputum and is currently available for clinical use. However, the analytical and clinical performance of this test has not been fully evaluated. The analytical limit of detection (LOD) of the Genedrive PCR amplification was tested with genomic DNA; the performance of the complete (sample processing plus amplification) system was tested by spiking M. tuberculosis mc 2 6030 cells into distilled water and M. tuberculosis -negative sputum. Specificity was tested using common respiratory pathogens and nontuberculosis mycobacteria. A clinical evaluation enrolled adults with suspected pulmonary tuberculosis, obtained three sputum samples from each participant, and compared the accuracy of the Genedrive to that of the Xpert MTB/RIF assay using M. tuberculosis cultures as the reference standard. The Genedrive assay had an LOD of 1 pg/μl (100 genomic DNA copies/reaction). The LODs of the system were 2.5 × 10 4 CFU/ml and 2.5 × 10 5 CFU/ml for cells spiked into water and sputum, respectively. False-positive rpoB probe signals were observed in 3/32 (9.4%) of the negative controls and also in few samples containing Mycobacterium abscessus , Mycobacterium gordonae , or Mycobacterium thermoresistibile . In the clinical study, among 336 analyzed participants, the overall sensitivities for the tuberculosis case detection of Genedrive, Xpert, and smear microscopy were 45.4% (95% confidence interval [CI], 35.2% to 55.8%), 91.8% (95% CI, 84.4% to 96.4%), and 77.3% (95% CI, 67.7% to 85.2%), respectively. The sensitivities of Genedrive and Xpert for the detection of smear-microscopy-negative tuberculosis were 0% (95% CI, 0% to 15.4%) and 68.2% (95% CI, 45.1% to 86.1%), respectively. The Genedrive assay did not meet performance standards recommended by the World Health Organization for a smear microscopy replacement tuberculosis test. Epistem is working on modifications to improve the assay.

Blood citrulline and intestinal fatty acid binding protein were determined as biomarkers for intestinal mucositis. Biomarker levels were correlated with corresponding serum 1,3-beta- d -glucan levels in 56 samples obtained from 33 cases with underlying hematological malignancies receiving induction chemotherapy. No correlation between biomarkers of intestinal mucositis and BDG levels was observed. (This study has been registered at ClinicalTrials.gov under registration no. NCT01576653.)

Molecular methods are often used for Neisseria gonorrhoeae detection, but complete definition of antimicrobial resistance (AMR) patterns still requires phenotypic tests. We developed an assay that both identifies N. gonorrhoeae and detects AMR determinants in clinical specimens., Molecular methods are often used for Neisseria gonorrhoeae detection, but complete definition of antimicrobial resistance (AMR) patterns still requires phenotypic tests. We developed an assay that both identifies N. gonorrhoeae and detects AMR determinants in clinical specimens. We designed a mismatch amplification mutation assay (MAMA)-based SYBR green real-time PCR targeting one N. gonorrhoeae-specific region (opa); mosaic penA alleles (Asp345 deletion [Asp345del], Gly545Ser) associated with decreased susceptibility to cephalosporins; and alterations conferring resistance to ciprofloxacin (GyrA Ser91Phe), azithromycin (23S rRNA A2059G and C2611T), and spectinomycin (16S rRNA C1192T). We applied the real-time PCR to 489 clinical specimens, of which 94 had paired culture isolates, and evaluated its performance by comparison with the performance of commercial diagnostic molecular and phenotypic tests. Our assay exhibited a sensitivity/specificity of 93%/100%, 96%/85%, 90%/91%, 100%/100%, and 100%/90% for the detection of N. gonorrhoeae directly from urethral, rectal, pharyngeal, cervical, and vaginal samples, respectively. The MAMA strategy allowed the detection of AMR mutations by comparing cycle threshold values with the results of the reference opa reaction. The method accurately predicted the phenotype of resistance to four antibiotic classes, as determined by comparison with the MIC values obtained from 94 paired cultures (sensitivity/specificity for cephalosporins, azithromycin, ciprofloxacin, and spectinomycin resistance, 100%/95%, 100%/100%, 100%/100%, and not applicable [NA]/100%, respectively, in genital specimens and NA/72%, NA/98%, 100%/97%, and NA/96%, respectively, in extragenital specimens). False-positive results, particularly for the penA Asp345del reaction, were observed predominantly in pharyngeal specimens. Our real-time PCR assay is a promising rapid method to identify N. gonorrhoeae and predict AMR directly in genital specimens, but further optimization for extragenital specimens is needed.

Accurate and rapid diagnosis is needed for timely intervention and clinical management of acute respiratory infections. This study evaluated performance characteristics of the Panther Fusion assay for the detection of influenza A virus (Flu A), influenza B virus (Flu B), respiratory syncytial virus (RSV), parainfluenza viruses 1 to 3 (Para 1 to 3), human metapneumovirus (hMPV), rhinovirus (RV), and adenovirus (Adeno) targets in comparison to those of the eSensor and Lyra assays using 395 nasopharyngeal (NP) and 104 lower respiratory tract (LRT) specimens. Based on the consensus positive result established (positive result in 2 of the 3 assays), the NP specimens for the Fusion and eSensor assays had 100% positive percent agreement (PPA) for all the analytes and the Lyra assays had 100% PPA for Flu A and Adeno analytes. A 100% negative percent agreement (NPA) was observed for all the Lyra analytes, whereas those for the Fusion targets ranged from 98.4 to 100% and those for the eSensor ranged from 99.4 to 100% for all the analytes except RV. For the LRT specimens, Fusion had 100% PPA and 100% NPA for all the targets except hMPV. There was a 100% PPA for eSensor analytes; the NPA ranged from 98 to 100%, except for RV. For the Lyra assays, the PPA ranged between 50 and 100%, while the NPA was 100% for all the targets except Adeno. The Fusion assay performed similarly to the eSensor assay for majority of the targets tested and provides laboratories with a fully automated random-access system to test for a broad array of viral respiratory pathogens.

A positive Toxoplasma immunoglobulin M (IgM) result is often interpreted as a marker of an acute infection. However, IgM can persist for several years, and Toxoplasma commercial IgM diagnostic test kits can yield a number of false-positive results. For these reasons, a chronic Toxoplasma infection can be erroneously classified as an acute infection, resulting in serious adverse consequences, especially in pregnant women, leading to emotional distress and unnecessary interventions, including termination of pregnancy. Interpretation of Toxoplasma serology at a reference laboratory can help differentiate a recently acquired infection from a chronic infection. Serological test results for 451 patients with positive Toxoplasma IgM and IgG test results obtained at nonreference laboratories (NRLs) that were referred to Palo Alto Medical Foundation Toxoplasma Serology Laboratory (PAMF-TSL) to determine whether the patient was acutely or chronically infected were retrospectively reviewed. PAMF-TSL results established that of the 451 patients, 335 (74%) had a chronic infection, 100 (22%) had an acute infection, and 7 (2%) were not infected, and for 9 (2%), results were indeterminate. Positive Toxoplasma IgM and IgG test results obtained at NRLs cannot accurately distinguish between acute and chronic infections. To do so, testing at reference laboratories is required, as mandated in 1997 in a letter from the Food and Drug Administration (FDA) to clinicians and laboratories in the United States.

The availability of reliable human immunodeficiency virus types 1 and 2 (HIV-1/2) rapid tests in resource-limited settings represents an important advancement in the accurate diagnosis of HIV infection and presents opportunities for implementation of effective prevention and treatment interventions among vulnerable populations. A study of the potential target populations for future HIV vaccine studies examined the prevalence of HIV infections at six selected sites in Nigeria and evaluated the use of two rapid diagnostic tests (RDTs) for HIV. The populations included market workers at sites adjacent to military installations and workers at highway settlements (truck stops) who may have a heightened risk of HIV exposure. Samples from 3,187 individuals who provided informed consent were tested in parallel using the Determine (DT) and Stat-Pak (SP) RDTs; discordant results were subjected to the Uni-Gold (UG) RDT as a tiebreaker. The results were compared to those of a third-generation enzyme immunoassay screen with confirmation of repeat reactive samples by HIV-1 Western blotting. One participant was HIV-2 infected, yielding positive results on both RDTs. Using the laboratory algorithm as a gold standard, we calculated sensitivities of 98.5% (confidence interval [CI], 97.1 to 99.8%) for DT and 98.1% (CI, 96.7 to 99.6%) for SP and specificities of 98.7% (CI, 98.3 −99.1%) for DT and 99.8% (CI, 99.6 to 100%) for SP. Similar results were obtained when the sites were stratified into those of higher HIV prevalence (9.4% to 22.8%) versus those of lower prevalence (3.2% to 7.3%). A parallel two-test algorithm requiring both DT and SP to be positive resulted in the highest sensitivity (98.1%; CI, 96.7 to 99.6%) and specificity (99.97%; CI, 99.9 to 100%) relative to those for the reference laboratory algorithm.

We report here the results of the diagnostic performances of Vitros Syphilis TPA (a chemiluminescence treponemal assay) compared with those of two treponemal enzyme immunoassays and of traditional versus reverse syphilis algorithms. Ease of use, automation, and high throughput make the Vitros Syphilis TPA assay a good choice for syphilis screening in high-volume laboratories.

HIV-1 entry into target cells influences several aspects of HIV-1 pathogenesis, including viral tropism, HIV-1 transmission and disease progression, and response to entry inhibitors. The evolution from CCR5- to CXCR4-using strains in a given human host is still unpredictable. Here we analyzed timing and predictors for coreceptor evolution among recently HIV-1-infected individuals. Proviral DNA was longitudinally evaluated in 66 individuals using Geno2pheno [coreceptor] . Demographics, viral load, CD4 + and CD8 + T cell counts, CCR5Δ32 polymorphisms, GB virus C (GBV-C) coinfection, and HLA profiles were also evaluated. Ultradeep sequencing was performed on initial samples from 11 selected individuals. A tropism switch from CCR5- to CXCR4-using strains was identified in 9/49 (18.4%) individuals. Only a low baseline false-positive rate (FPR) was found to be a significant tropism switch predictor. No minor CXCR4-using variants were identified in initial samples of 4 of 5 R5/non-R5 switchers. Logistic regression analysis showed that patients with an FPR of >40.6% at baseline presented a stable FPR over time whereas lower FPRs tend to progressively decay, leading to emergence of CXCR4-using strains, with a mean evolution time of 27.29 months (range, 8.90 to 64.62). An FPR threshold above 40.6% determined by logistic regression analysis may make it unnecessary to further determine tropism for prediction of disease progression related to emergence of X4 strains or use of CCR5 antagonists. The detection of variants with intermediate FPRs and progressive FPR decay over time not only strengthens the power of Geno2pheno in predicting HIV tropism but also indirectly confirms a continuous evolution from earlier R5 variants toward CXCR4-using strains. IMPORTANCE The introduction of CCR5 antagonists in the antiretroviral arsenal has sparked interest in coreceptors utilized by HIV-1. Despite concentrated efforts, viral and human host features predicting tropism switch are still poorly understood. Limited longitudinal data are available to assess the influence that these factors have on predicting tropism switch and disease progression. The present study describes longitudinal tropism evolution in a group of recently HIV-infected individuals to determine the prevalence and potential correlates of tropism switch. We demonstrated here that a low baseline FPR determined by the Geno2pheno [coreceptor] algorithm can predict tropism evolution from CCR5 to CXCR4 coreceptor use.

This study was undertaken to examine the performance of the Fungitell β-glucan (BG) assay, to compare it with that of the galactomannan (GM) test for the diagnosis of invasive aspergillosis (IA) in patients with hematological malignancies, and to examine the rates of false-positive BG and GM test results due to β-lactam antibiotics among sera of patients with Gram-positive or Gram-negative bacteremia and selected sera with false-positive results from the GM test. Serum samples from 105 patients with proven ( n = 14) or probable ( n = 91) IA, 97 hematology patients at risk for invasive fungal infections, 50 healthy blood donors, and 60 patients with bacteremia were used to study the sensitivities and specificities of the assays. The GM test was more specific than the BG assay (97% versus 82%, respectively; P = 0.0001) and the BG assay was more sensitive than the GM test (81% versus 49%, respectively; P < 0.0001) for IA diagnosis. The study of 49 separate batches of β-lactam antibiotics showed high and very similar rates of false-positive results for the GM and BG assays (29 and 33%, respectively; P = 0.82) but with an almost complete lack of concordance between the 2 assays. For patients with bacteremia, the rate of false-positive results was much higher with the BG test than with the GM test (37% versus 2%, respectively; P < 0.0001), with no significant difference between Gram-positive and Gram-negative bacteremia. In conclusion, the BG test may be useful for the diagnosis of IA because of its high sensitivity in comparison with the GM test, but the overall benefit of this assay remains limited because of its inadequate specificity and its cost.

The novel influenza A(H1N1)pdm09 virus caused an influenza pandemic in 2009. IgM, IgG, and IgA antibody responses to A(H1N1)pdm09 hemagglutinin (HA) following A(H1N1)pdm09 virus infection were analyzed to understand antibody isotype responses. Age-matched control sera collected from U.S. residents in 2007 and 2008 were used to establish baseline levels of cross-reactive antibodies. IgM responses often used as indicators of primary virus infection were mainly detected in young patient groups (≤5 years and 6 to 15 years old), not in older age groups, despite the genetic and antigenic differences between the HA of A(H1N1)pdm09 virus and pre-2009 seasonal H1N1 viruses. IgG and IgA responses to A(H1N1)pdm09 HA were detected in all age groups of infected persons. In persons 17 to 80 years old, paired acute- and convalescent-phase serum samples demonstrated ≥4-fold increases in the IgG and IgA responses to A(H1N1)pdm09 HA in 80% and 67% of A(H1N1)pdm09 virus-infected persons, respectively. The IgG antibody response to A(H1N1)pdm09 HA was cross-reactive with HAs from H1, H3, H5, and H13 subtypes, suggesting that infections with subtypes other than A(H1N1)pdm09 might result in false positives by enzyme-linked immunosorbent assay (ELISA). Lower sensitivity compared to hemagglutination inhibition and microneutralization assays and the detection of cross-reactive antibodies against homologous and heterologous subtype are major drawbacks for the application of ELISA in influenza serologic studies.

The Shiga toxin-producing Escherichia coli (STEC) strains, including those of O157:H7 and the “big six” serogroups (i.e., serogroups O26, O45, O103, O111, O121, and O145), are a group of pathogens designated food adulterants in the United States. The relatively conserved nature of c lustered r egularly i nterspaced s hort p alindromic r epeats (CRISPRs) in phylogenetically related E. coli strains makes them potential subtyping markers for STEC detection, and a quantitative PCR (qPCR)-based assay was previously developed for O26:H11, O45:H2, O103:H2, O111:H8, O121:H19, O145:H28, and O157:H7 isolates. To better evaluate the sensitivity and specificity of this qPCR method, the CRISPR loci of 252 O157 and big-six STEC isolates were sequenced and analyzed along with 563 CRISPR1 and 624 CRISPR2 sequences available in GenBank. General conservation of spacer content and order was observed within each O157 and big-six serogroup, validating the qPCR method. Meanwhile, it was found that spacer deletion, the presence of an insertion sequence, and distinct alleles within a serogroup are sources of false-negative reactions. Conservation of CRISPR arrays among isolates expressing the same flagellar antigen, specifically, H7, H2, and H11, suggested that these isolates share an ancestor and provided an explanation for the false positives previously observed in the qPCR results. An analysis of spacer distribution across E. coli strains provided limited evidence for temporal spacer acquisition. Conversely, comparison of CRISPR sequences between strains along the stepwise evolution of O157:H7 from its O55:H7 ancestor revealed that, over this ∼7,000-year span, spacer deletion was the primary force generating CRISPR diversity.

Whole-genome sequence (WGS) data are commonly used to design diagnostic targets for the identification of bacterial pathogens. To do this effectively, genomics databases must be comprehensive to identify the strict core genome that is specific to the target pathogen. As additional genomes are analyzed, the core genome size is reduced and there is erosion of the target-specific regions due to commonality with related species, potentially resulting in the identification of false positives and/or false negatives., IMPORTANCE A comparative analysis of 1,130 Burkholderia genomes identified unique markers for many named species, including the human pathogens B. pseudomallei and B. mallei. Due to core genome reduction and signature erosion, only 38 targets specific to B. pseudomallei/mallei were identified. By using only public genomes, a larger number of markers were identified, due to undersampling, and this larger number represents the potential for false positives. This analysis has implications for the design of diagnostics for other species where the genomic space of the target and/or closely related species is not well defined.

Immunoglobulin M (IgM) tests have clear clinical utility but also suffer disproportionately from false-positive results, which in turn can lead to misdiagnoses, inappropriate therapy, and premature closure of a diagnostic workup. Despite numerous reports in the literature, many clinicians and laboratorians remain unaware of this issue. In this brief review, a series of virology case examples is presented. However, a false-positive IgM can occur with any pathogen. Thus, when an accurate diagnosis is essential for therapy, prognosis, infection control, or public health, when the patient is sick enough to be hospitalized, or when the clinical or epidemiologic findings do not fit, IgM detection should not be accepted as a stand-alone test. Rather, whenever possible, the diagnosis should be confirmed by other means, including testing of serial samples and the application of additional test methods.

Chagas disease has spread to areas that are nonendemic for the disease with human migration. Since no single reference standard test is available, serological diagnosis of chronic Chagas disease requires at least two tests. New-generation techniques have significantly improved the accuracy of Chagas disease diagnosis by the use of a large mixture of recombinant antigens with different detection systems, such as chemiluminescence. The aim of the present study was to assess the overall accuracy of a new-generation kit, the Architect Chagas (cutoff, ≥1 sample relative light units/cutoff value [S/CO]), as a single technique for the diagnosis of chronic Chagas disease. The Architect Chagas showed a sensitivity of 100% (95% confidence interval [CI], 99.5 to 100%) and a specificity of 97.6% (95% CI, 95.2 to 99.9%). Five out of six false-positive serum samples were a consequence of cross-reactivity with Leishmania spp., and all of them achieved results of Leishmania species. The application of this proposal would result in important savings in the cost of Chagas disease diagnosis and therefore in the management and control of the disease.

In many clinical microbiology laboratories, nucleic acid amplification tests such as PCR have become the routine methods for the diagnosis of pertussis. While PCR has greatly increased the ability of laboratories to detect Bordetella pertussis infections, it has also been associated with false-positive results that can, given the tendency of B. pertussis to cause outbreaks, result in unnecessary and costly control measures. The species specificity of Bordetella gene targets and their number of copies per genome greatly impact the performance characteristics of nucleic acid amplification tests for B. pertussis . It is crucial that laboratorians recognize these characteristics, to limit false-positive test results and prevent pseudo-outbreaks.

The diagnosis of schistosomiasis in individuals from countries where the disease is not endemic is challenging, and few data are available on the accuracy of serological diagnosis in those patients. We evaluated the performance of eight serological assays, including four commercial kits, in the diagnosis of imported schistosomiasis in individuals from areas where the disease is not endemic, including six enzyme-linked immunosorbent assays using three different antigens, an indirect hemagglutination assay, and an indirect immunofluorescent-antibody test. To analyze the assays, we used a total of 141 serum samples, with 121 derived from patients with various parasitic infections (among which were 37 cases of schistosomiasis) and 20 taken from healthy volunteers. The sensitivity values for detection of schistosomiasis cases ranged from 41% to 78% and were higher for Schistosoma mansoni than for S. haematobium infections. Specificity values ranged from 76% to 100%; false-positive results were most frequent for samples from patients with cestode infections. By combining two or more tests, sensitivity improved markedly and specificity decreased only moderately. Serological tests are useful instruments for diagnosing imported schistosomiasis in countries where the disease is not endemic, but due to limitations in test sensitivities, we recommend the use of two or more assays in parallel.

This study compared the three most commonly used assays for detecting Cryptosporidium sp. infections in cell culture: immunofluorescent antibody and microscopy assay (IFA), PCR targeting Cryptosporidium sp.-specific DNA, and reverse transcriptase PCR (RT-PCR) targeting Cryptosporidium sp.-specific mRNA. Monolayers of HCT-8 cells, grown in 8-well chamber slides or 96-well plates, were inoculated with a variety of viable and inactivated oocysts to assess assay performance. All assays detected infection with low doses of flow cytometry-enumerated Cryptosporidium parvum oocysts, including infection with one oocyst and three oocysts. All methods also detected infection with Cryptosporidium hominis . The RT-PCR assay, IFA, and PCR assay detected infection in 23%, 25%, and 51% of monolayers inoculated with three C. parvum oocysts and 10%, 9%, and 16% of monolayers inoculated with one oocyst, respectively. The PCR assay was the most sensitive, but it had the highest frequency of false positives with mock-infected cells and inactivated oocysts. IFA was the only infection detection assay that did not produce false positives with mock-infected monolayers. IFA was also the only assay that detected infections in all experiments with spiked oocysts recovered from Envirochek capsules following filtration of 1,000 liters of treated water. Consequently, cell culture with IFA detection is the most appropriate method for routine and sensitive detection of infectious Cryptosporidium parvum and Cryptosporidium hominis in drinking water.

Nucleic acid amplification techniques permitting sensitive and rapid screening in patients at risk for invasive fungal infections are an important addition to conventional fungal diagnostic methods. However, contamination with fungal DNA may be a serious threat to the validity of fungal amplification-based assays. Besides rigorous handling procedures to avoid false-positive test results from exogenous sources, we have implemented protocols for comprehensive assessment of fungal contamination in all materials involved in the analytical process. Traces of fungal DNA were found in different commercially available PCR reagents, including lyophilized primers, TaqMan probes, and master mix solutions. These contaminants resulted in a considerable rate of false-positive tests in panfungal real-time PCR analysis. To address this problem, we have established a decontamination protocol based on the activity of a double-strand specific DNase. Using this approach, we have significantly reduced the frequency of false-positive test results attributable to contaminated reagents. On the basis of our findings, we strongly recommend routine monitoring of all reagents used in fungal PCR assays for the presence of relevant contaminants. As long as fungal-grade reagents are not readily available, pretreatment methods facilitating elimination of fungal DNA are critical for reducing the risk of false-positive results in highly sensitive molecular fungal detection assays.

Brucellosis is a disease with worldwide distribution affecting animals and human beings. Brucella abortus is the causative agent of bovine brucellosis. The cross-reactions of currently available diagnostic procedures for B. abortus infection result in false-positive reactions, which make the procedures unreliable. These tests are also unable to differentiate Brucella-infected and -vaccinated animals. The present work is focused on the use of a nonlipopolysaccharide (LPS) diagnostic antigen, a recombinant 10-kDa (r10-kDa) protein of B. abortus, for specific diagnosis of brucellosis. The purified recombinant protein was used as a diagnostic antigen in plate enzyme-linked immunosorbent assay (p-ELISA) format to screen 408 bovine serum samples (70 presumptively negative, 308 random, and 30 vaccinated), and the results were compared with those of the Rose Bengal plate agglutination test (RBPT) and the standard tube agglutination test (STAT). Statistical analysis in presumptive negative samples revealed 100 and 98.41% specificity of p-ELISA with RBPT and STAT, and an agreement of 91.43% with the tests using Cohen’s kappa statistics. In random samples, the agreement of p-ELISA was 77.92% and 80.52% with RBPT and STAT, respectively. p-ELISA investigation of vaccinated samples reported no false-positive results, whereas RBPT and STAT reported 30% and 96.6% false-positive results, respectively. The data suggest that p-ELISA with r10-kDa protein may be a useful method for diagnosis of bovine brucellosis. Furthermore, p-ELISA may also be used as a tool for differentiating Brucella-vaccinated and naturally infected animals. Brucellosis, a contagious disease primarily affecting animals, is caused by members of the genus Brucella, namely, Brucella abortus (cattle, bison, and buffalo), B. melitensis (goats and sheep), B. suis (swine), B. canis (dogs), B. ovis (sheep), and B. neotomae (rodents). Bovine brucellosis is caused by biovars of B. abortus. The disease is asymptomatic in animals that have not conceived. Following infection with B. abortus, pregnant adult females develop placentitis, resulting in abortion between the fifth and ninth months of pregnancy and infertility. Adult male cattle may develop orchitis, leading to infertility. Brucellosis has zoonotic potential in terms of its transmissibility to human beings attending infected livestock, showing symptoms in the form of low-grade undulant fever, night sweats, early fatigue, joint pain leading to spondylitis, and orchitis, and it is commonly known as “undulant fever,” “Mediterranean fever,” or “Malta fever” (7). The disease remains a public health problem and results in severe economic losses in

The effects of the recent vaccinations against bluetongue virus serotype 1 (BTV-1) and BTV-8 in Europe on the reliability of enzyme-linked immunosorbent assays (ELISAs) currently used for diagnosis of small-ruminant lentivirus (SRLV) infection were examined. Primary vaccination against BTV-8 in goats induced an increase in reactivity that did not exceed 3 months in a whole-virus indirect ELISA and a competitive ELISA based on the gp135 glycoprotein. Subsequent BTV-1/8 vaccination extended the time scale of false-positive reactivity for up to 6 months. These results are of relevance for SRLV-monitoring programs.

Piperacillin-tazobactam (PTZ) is known to cause false-positive results in the Platelia Aspergillus enzyme-linked immunoassay (EIA), due to contamination with galactomannan (GM). We tested 32 lots of PTZ and 27 serum specimens from patients receiving PTZ. GM was not detected in the lots of PTZ; one serum specimen (3.7%) was positive. PTZ formulations commonly used in the United States today appear to be a rare cause for false-positive GM results.

Recreational water quality is currently monitored using culture-based methods that require 18 to 96 h for results. Quantitative PCR (QPCR) methods that can be completed in less than 2 h have been developed, but they could yield different results than the conventional methods. We present two studies in which samples were processed simultaneously for Enterococcus spp. and Escherichia coli using two culture-based methods (EPA method 1600 and Enterolert/Colilert-18) and QPCR. The proprietary QPCR assays targeted the 23S rRNA ( Enterococcus spp.) and uidA ( E. coli ) genes and were conducted using lyophilized beads containing all reagents. In the first study, the QPCR method developers processed 54 blind samples that were inoculated with sewage or pure cultures or were ambient beach samples. The second study involved 163 samples processed by water quality personnel. The correlation between results of QPCR and EPA 1600 during the first study ( r 2 ) was 0.69 for Enterococcus spp., which was less than that observed between the culture-based methods ( r 2 , 0.87). During the second study, the correlations were similar. No false positives occurred in either study when QPCR-based assays were used with blank samples. Levels of reproducibility measured through coefficients of variation were similar for results by Enterococcus QPCR and culture-based methods during both studies but were higher for E. coli QPCR results in the first study. Regarding the concentration at which beach management decisions are issued in the State of California, the agreement between results of Enterococcus QPCR and EPA method 1600 was 88%, compared to 94% agreement between EPA method 1600 and Enterolert. The beach management decision agreement between E. coli QPCR and Colilert-18 was 94%. The samples showing disagreement suggested an underestimation bias for QPCR.

The purpose of this study was to evaluate the performance of laboratories for the detection and quantification of human herpesvirus 6 (HHV-6) by an external quality assessment (EQA) evaluation. The HHV-6 EQA panel consisted of eight samples containing various concentrations of HHV-6 type A (strain GS) or type B (strain Z29), two samples containing other herpesviruses (i.e., human cytomegalovirus [HCMV] and Epstein-Barr virus [EBV]), and two HHV-6-negative samples. Panel samples were prepared in human plasma, heat inactivated, and lyophilized. Panel distribution, data management, and analysis were coordinated by Quality Control for Molecular Diagnostics (QCMD), Glasgow, United Kingdom. Fifty-one laboratories participated and submitted 57 data sets. Eleven (19.3%) data sets were generated using conventional in-house assays, 11 (19.3%) data sets using commercial real-time PCR assays, and 35 (61.4%) data sets using in-house real-time PCR assays. The presence of HHV-6 DNA at viral loads exceeding 6,000 copies/ml was detected by all participants, and over 80% of the participants still reported correct qualitative results for the sample containing just over 200 copies/ml. The false-positivity rate was 1.8% for both the negative samples and the samples containing HCMV or EBV DNA. The majority (23/33; 69.7%) of quantitative data sets were generated using in-house real-time PCR assays. The standard deviations of the geometric means of the samples ranged from 0.5 to 0.7 log 10 . The results of this first international EQA demonstrate encouraging analytical sensitivity for the detection of HHV-6-DNA in human plasma, although we observed extensive interlaboratory variation of quantitative HHV-6 DNA results. Standardization needs to be improved to allow further elucidation of the clinical significance of HHV-6 loads.

An epitope-blocking enzyme-linked immunosorbent assay (b-ELISA) was evaluated for the diagnosis of West Nile virus (WNV) infections in humans. Sera from patients diagnosed with WNV infections from an outbreak in 2003 in Colorado and from patients diagnosed with dengue virus infections from Mexico and Thailand were tested with the b-ELISA. The b-ELISAs were performed using the WNV-specific monoclonal antibody (MAb) 3.1112G and the flavivirus-specific MAb 6B6C-1. Although the WNV-specific b-ELISA was effective in diagnosing WNV infections in humans from Colorado, it was not efficacious for diagnosing WNV infections in serum specimens from Mexico and Thailand. In serum specimens from patients from Colorado, the WNV b-ELISA and the WNV plaque reduction neutralization test showed an overall agreement of 91%. The sensitivity and specificity of the WNV b-ELISA were 89% and 92%, respectively, with a false-positive rate of 5%, based on receiver operating characteristic analysis. In contrast, false-positive rate results in specimens from the countries of Mexico and Thailand, where flaviviruses are endemic, were 79% and 80%, presumably due to the presence of antibodies resulting from previous dengue virus infections in Mexico and/or Japanese encephalitis virus infections or vaccination in Thailand. Thus, in regions where people have experienced previous or multiple flavivirus infections, the use of the b-ELISA for WNV diagnosis is contraindicated.

The worldwide increase in the occurrence and dissemination of KPC β-lactamases among gram-negative pathogens makes critical the early detection of these enzymes. Boronic acid disk tests using different antibiotic substrates were evaluated for detection of KPC-possessing Klebsiella pneumoniae isolates. A total of 57 genotypically confirmed KPC-possessing K. pneumoniae isolates with varying carbapenem MICs were examined. To measure the specificity of the tests, 106 non-KPC-possessing isolates (89 K. pneumoniae and 17 Escherichia coli isolates) were randomly selected among those exhibiting reduced susceptibility to cefoxitin, expanded-spectrum cephalosporins, or carbapenems. As many as 56, 53, and 40 of the non-KPC-possessing isolates harbored extended-spectrum β-lactamases, metallo-β-lactamases, and plasmid-mediated AmpC β-lactamases, respectively. By use of CLSI methodology and disks containing imipenem, meropenem, or cefepime, either alone or in combination with 400 μg of boronic acid, all 57 KPC producers gave positive results (sensitivity, 100%) whereas all 106 non-KPC producers were negative (specificity, 100%). The meropenem duplicate disk with or without boronic acid demonstrated the largest differences in inhibition zone diameters between KPC producers and non-KPC producers. By use of disks containing ertapenem, all isolates were correctly differentiated except for five AmpC producers that gave false-positive results (sensitivity, 100%; specificity, 95.3%). These practical and simple boronic acid disk tests promise to be very helpful for the accurate differentiation of KPC-possessing K. pneumoniae isolates, even in regions where different broad-spectrum β-lactamases are widespread.

Hybrid Capture 2 (hc2), a clinical test for carcinogenic human papillomavirus (HPV) DNA, has proven to be a sensitive but only modestly specific predictor of cervical precancer and cancer risk. Some of its nonspecificity for clinical end points can be ascribed to cross-reactivity with noncarcinogenic HPV genotypes. However, the reference genotyping tests that have been used for these comparisons are also imperfect. We therefore sought to describe further the HPV genotype specificity of hc2 by comparing the hc2 results to paired results from two related PGMY09/11 L1 primer-based HPV genotyping assays: Linear Array (LA) and its prototype predecessor, the line blot assay (LBA). LA and LBA results were considered separately and combined (detection by either assay or both assays) for 37 individual HPV genotypes and HPV risk group categories (carcinogenic HPV > noncarcinogenic HPV > negative). Baseline specimens from 3,179 of 3,488 (91.5%) women referred to ALTS (a clinical trial to evaluate the management strategies for women with atypical squamous cells of undetermined significance [ASCUS] or low-grade squamous intraepithelial lesions) because of an ASCUS Papanicolaou smear were tested by all three assays. Among single-genotype infections with genotypes targeted by hc2 as detected by either PCR assay, HPV genotype 35 (HPV35) (86.4%), HPV56 (84.2%), and HPV58 (76.9%) were the most likely to test positive by hc2. Among single-genotype infections with genotypes not targeted by hc2 as detected by either assay, HPV82 (80.0%), HPV66 (60.0%) (recently classified as carcinogenic), HPV70 (59.1%), and HPV67 (56.3%) were the most likely to test positive by hc2. Among women who tested negative for carcinogenic HPV by both PCR tests and were positive for noncarcinogenic HPV by either test, 28% of women were hc2 positive. Conversely, 7.8% of all hc2-positive results in this population were due to cross-reactivity of hc2 with untargeted, noncarcinogenic HPV genotypes. In conclusion, hc2 cross-reacts with certain untargeted, noncarcinogenic HPV genotypes that are phylogenetically related to the targeted genotypes, but the degree of cross-reactivity may be less than previously reported.

Signal-to-noise-ratio (SNR) thresholds for microarray data analysis were experimentally determined with an oligonucleotide array that contained perfect-match (PM) and mismatch (MM) probes based upon four genes from Shewanella oneidensis MR-1. A new SNR calculation, called the signal-to-both-standard-deviations ratio (SSDR), was developed and evaluated, along with other two methods, the signal-to-standard-deviation ratio (SSR) and the signal-to-background ratio (SBR). At a low stringency, the thresholds of the SSR, SBR, and SSDR were 2.5, 1.60, and 0.80 with an oligonucleotide and a PCR amplicon as target templates and 2.0, 1.60, and 0.70 with genomic DNAs as target templates. Slightly higher thresholds were obtained under high-stringency conditions. The thresholds of the SSR and SSDR decreased with an increase in the complexity of targets (e.g., target types) and the presence of background DNA and a decrease in the compositions of targets, while the SBR remained unchanged in all situations. The lowest percentage of false positives and false negatives was observed with the SSDR calculation method, suggesting that it may be a better SNR calculation for more accurate determination of SNR thresholds. Positive spots identified by SNR thresholds were verified by the Student t test, and consistent results were observed. This study provides general guidance for users to select appropriate SNR thresholds for different samples under different hybridization conditions.

We compared the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture with BBL CHROMagar MRSA for nasal surveillance among 602 arrestees from the Baltimore City Jail. The sensitivity and specificity were 88.5% and 91.0%, respectively, and after secondary analysis using enrichment broth, they were 89.0% and 91.7%, respectively. Twenty-three of 42 false-positive PCR lysates contained methicillin-susceptible S. aureus .

We investigated in vitro whether storage of blood samples influences the time to positivity used for the calculation of the differential time to positivity (DTP) and the results of the Gram stain-acridine orange leukocyte Cytospin (AOLC) test. A 24-hour storage of blood samples at room temperature may lead to false-negative DTP and false-positive Gram stain-AOLC test results, whereas storage at 4°C does not.

More than 2 decades of developments in the field have led to a wide variety of test kits available for addressing the different needs of surveillance, diagnosis, and monitoring of human immunodeficiency virus (HIV) infection and antiretroviral therapy ([20][1], [23][2]). These test kits are based on

Since the introduction of West Nile virus (WNV) in the United States in 1999, several assays have become commercially available to detect antibodies against WNV. Capture enzyme-linked immunosorbent assays (ELISAs) for the detection of WNV-specific immunoglobulin M (IgM) have been approved by the Food and Drug Administration for clinical testing and are available from Focus Diagnostics and PanBio, Inc. The Focus Diagnostics IgM capture ELISA utilizes a background subtraction protocol in order to detect nonspecific reactivity due to rheumatoid factor, heterophile antibodies, or other interfering substances. A background subtraction procedure is not currently recommended for the PanBio IgM capture ELISA. In previous experiments, we determined the agreement, sensitivity, and specificity of the PanBio first-generation IgM capture ELISA compared to an immunofluorescence assay and the Centers for Disease Control and Prevention's IgM capture ELISA. The PanBio assay has since been reformulated to improve the specificity of the assay. We evaluated the reformulated PanBio assay with and without an antigen subtraction procedure and compared the results to the Focus IgM capture ELISA. Agreement, sensitivity, and specificity of the PanBio assay were, respectively, 85%, 95%, and 76% without the subtraction protocol and 94%, 95%, and 93% with the subtraction protocol. In general, when the subtraction protocol was applied to the PanBio IgM capture ELISA, there was a reduction in some, but not all, false-positive results. We suggest that all WNV IgM assays be standardized with a procedure such as background subtraction to eliminate nonspecific reactivity that may cause false-positive results.

In order to demonstrate that cells of Candida spp. may show considerable nonspecific agglutination in latex agglutination tests, 150 clinical and reference isolates of 12 yeast species were systematically studied by applying various test parameters. In fact, 40 (26.7%) of these isolates revealed nonspecific results, significantly associated with the time allowed for agglutination.

We conducted retrospective, comparative analyses of contamination rates for cultures of blood obtained in the emergency rooms of Muhimbili National Hospital (MNH) in Dar es Salaam, Tanzania; Lilongwe Central Hospital (LCH) in central Malawi; and the Duke University Medical Center (DUMC) in the United States. None of the emergency room patients had indwelling intravascular devices at the time that the blood samples for cultures were obtained. In addition, we reviewed the contamination rates for a cohort of patients already hospitalized in the DUMC inpatient medical service, most of whom had indwelling intravascular devices. The bloodstream infection rates among the patients at MNH ( n = 513) and LCH ( n = 486) were similar (∼28%); the contamination rates at the two hospitals were 1.3% (7/513) and 0.8% (4/486), respectively. Of 54 microorganisms isolated from cultures of blood collected in the DUMC emergency room, 26 (48%) were identified as skin contaminants. Cultures of blood collected in the DUMC emergency room were significantly more likely to yield growth of contaminants than the cultures of blood collected in the emergency rooms at MNH and LCH combined (26/332 versus 11/1,003; P < 0.0001) or collected in the DUMC inpatient medical service (26/332 versus 7/283; P < 0.01). For the MNH and LCH blood cultures, lower contamination rates were observed when skin was disinfected with isopropyl alcohol plus tincture of iodine rather than isopropyl alcohol plus povidone-iodine. In conclusion, blood culture contamination was minimized in sub-Saharan African hospitals with substantially limited resources through scrupulous attention to aseptic skin cleansing and improved venipuncture techniques. Application of these principles when blood samples for culture are obtained in U.S. hospital emergency rooms should help mitigate blood culture contamination rates and the unnecessary microbiology workup of skin contaminants.

Forty-four intravenous antimicrobials were tested for the presence of (1→3)-β- d -glucan (BG). Colistin, ertapenem, cefazolin, trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam tested positive for BG at reconstituted-vial concentrations but not when diluted to usual maximum plasma concentrations. False-positive BG assays may occur when some antimicrobials are administered; however, this needs to be confirmed.

Malaria may impact upon human immunodeficiency virus (HIV) test results. We evaluated two HIV enzyme immunoassays (EIAs) by testing 1,965 Ugandans with malaria. We found poor positive predictive values (53% and 76%), particularly with younger age. Combining EIAs eliminated false positives but missed 21% of true positives. Performance of HIV EIAs in malaria may be unsatisfactory.

To evaluate the reactivity of the recombinant proteins expressed in Escherichia coli strain BL21(DE3), a Western blot assay was performed by using a panel of 78 serum samples obtained, respectively, from convalescent-phase patients infected with severe acute respiratory syndrome-associated coronavirus (SARS-CoV) (30 samples) and from healthy donors (48 samples). As antigen for detection of SARS-CoV, the nucleocapsid protein (N) showed high sensitivity and strong reactivity with all samples from SARS-CoV patients and cross-reacted with all serum samples from healthy subjects, with either those obtained from China (10 samples) or those obtained from France (38 serum samples), giving then a significant rate of false positives. Specifically, our data indicated that the two subunits, S1 (residues 14 to 760) and S2 (residues 761 to 1190), resulted from the divided spike reacted with all samples from SARS-CoV patients and without any cross-reactivity with any of the healthy serum samples. Consequently, these data revealed the nonspecific nature of N protein in serodiagnosis of SARS-CoV compared with the S1 and S2, where the specificity is of 100%. Moreover, the reported results indicated that the use of one single protein as a detection antigen of SARS-CoV infection may lead to false-positive diagnosis. These may be rectified by using more than one protein for the serodiagnosis of SARS-CoV.

To increase testing efficiency, a microsphere-based multianalyte immune detection (MAID) system was developed to measure serum immunoglobulin G (IgG) and IgA recognizing two Bordetella pertussis antigens, pertussis toxin (PT) and filamentous hemagglutinin antigen (FHA). The assay was performed as two separate duplexes. One duplex measured IgG to PT and FHA, and the other measured IgA to PT and FHA. The two duplexes were then combined and analyzed as a tetraplex. The MAID system and an in-house enzyme-linked immunosorbent assay (ELISA) system were used to evaluate 100 sera from blood donors and 220 consecutive sera submitted for B. pertussis antibody testing. For both the MAID and ELISA systems, antibody levels were defined as increased if greater than the blood donor group 95th percentile value. The qualitative concordance rates between MAID and ELISA results for the 220 consecutively submitted sera were as follows: PT IgG, 99%; PT IgA, 94%; FHA IgG, 93%; FHA IgA, 94%. The overall concordance rate was 95% (836 of 880 result sets). For 29 of 44 (66%) discordant result sets, the discordant MAID result was supported by the MAID and ELISA results for other B. pertussis antibodies. The MAID and in-house ELISA systems were also used to evaluate 20 sera previously tested for pertussis antibodies at a pertussis vaccine research laboratory; MAID results for all four analytes did not significantly differ from results obtained by the research laboratory. These findings show that antibodies to B. pertussis antigens can be measured easily and accurately using a tetraplex microsphere system.