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The Omicron (B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the last variant of concern (VOC) identified to date. Compared to whole-genome or gene-specific sequencing methods, reverse-transcription PCR assays may be a simpler approach to study VOCs. We used a point-of-care COVID-19 diagnostic PCR assay to detect the Omicron SARS-CoV-2 variant in the respiratory tract samples of COVID-19 patients who had tested positive for SARS-CoV-2 RNA between April 2021 and January 2022. Sequencing analyses had shown that 87 samples were positive for the Omicron variant and 43 samples were positive for a non-Omicron variant (Delta, 18 samples; Alpha, 13 samples; Gamma, 10 samples; Beta, 1 sample; or Epsilon, 1 sample). According to results by the PCR assay, whose primers anneal a nucleocapsid (N) gene region that comprises the E31/R32/S33 deletion (also termed the del31/33 mutation), we found that N gene target failure/dropout (i.e., a negative/low result) occurred in 86 (98.8%) of 87 Omicron variant-positive samples tested. These results were assessed in relation to those of the spike (S) gene, which expectedly, was detected in all (100%) 130 samples. A total of 43 (100%) of 43 Delta, Alpha, Gamma, Beta, or Epsilon variant-positive samples had a positive result with the N gene. Importantly, in 86 of 87 Omicron variant-positive samples, the del31/33 mutation was detected together with a P13L mutation, which was, instead, detected alone in the Omicron variant-positive sample that had a positive N-gene result. IMPORTANCE Rapid detection of the Omicron SARS-CoV-2 variant in patients' respiratory tract samples may influence therapeutic choices, because this variant is known to escape from certain monoclonal antibodies. Our findings strengthen the importance of manufacturers' efforts to improve the existing COVID-19 diagnostic PCR assays and/or to develop novel variant-specific PCR assays. Furthermore, our findings show that only a small fraction of SARS-CoV-2-positive samples may require whole-genome sequencing analysis, which is still crucial to validate PCR assay results. We acknowledge that the emergence of novel variants containing mutations outside the PCR assay target region could, however, allow an assay to work as per specifications without being able to identify a SARS-CoV-2-positive sample as a variant. Future work and more experience in this topic will help to reduce the risk of misidentification of SARS-CoV-2 variants that is unavoidable when using the current PCR assays.

Objectives: Compared to RT-PCR, lower performance of antigen detection assays, including the Lumipulse G SARS-CoV-2 Ag assay, may depend on specific testing scenarios., Methods: We tested 594 nasopharyngeal swab samples from individuals with COVID-19 (RT-PCR cycle threshold [Ct] values ≤ 40) or non-COVID-19 (Ct values >40) diagnoses. RT-PCR positive samples were assigned to diagnostic, screening, or monitoring groups of testing., Results: With a limit of detection of 1.2 × 10 4 SARS-CoV-2 RNA copies/mL, Lumipulse showed positive percent agreement (PPA) of 79.9% (155/194) and negative percent agreement of 99.3% (397/400), whereas PPAs were 100% for samples with Ct values of <18 or 18-<25 and 92.5% for samples with Ct values of 25-<30. By three groups, Lumipulse showed PPA of 87.0% (60/69), 81.1% (43/53), or 72.2% (52/72), respectively, whereas PPA was 100% for samples with Ct values of <18 or 18-<25, and was 94.4, 80.0, or 100% for samples with Ct values of 25-<30, respectively. Additional testing of RT-PCR positive samples for SARS-CoV-2 subgenomic RNA showed that, by three groups, PPA was 63.8% (44/69), 62.3% (33/53), or 33.3% (24/72), respectively. PPAs dropped to 55.6, 20.0, or 41.7% for samples with Ct values of 25-<30, respectively. All 101 samples with a subgenomic RNA positive result had a Lumipulse assay's antigen positive result, whereas only 54 (58.1%) of remaining 93 samples had a Lumipulse assay's antigen positive result., Conclusions: Lumipulse assay was highly sensitive in samples with low RT-PCR Ct values, implying repeated testing to reduce consequences of false-negative results., (© 2021 Giulia Menchinelli et al., published by De Gruyter, Berlin/Boston.)

The increasing COVID-19 widespread has created the necessity to assess the diagnostic accuracy of newly introduced (RT-PCR based) assays for SARS-CoV-2 RNA detection in respiratory tract samples. We compared the results of the Allplex™ 2019-nCoV assay with those of the Simplexa™ COVID-19 Direct assay and the Quanty COVID-19 assay, respectively, all performed on 125 nasal/oropharyngeal swab samples of patients with COVID-19 suspicion. Fifty-four samples were positive, and 71 were negative with the Allplex™ assay, whereas 47 of 54 samples were also positive with the Simplexa™ assay. The Quanty assay detected 55 positive samples, including the 54 positive samples with the Allplex™ assay and 1 sample that was Allplex™ negative but Simplexa™ positive. Using a consensus result criterion as the reference standard allowed to resolve the eight samples with discordant results (one Allplex™ negative and seven Simplexa™ negative) as truly false negative. Interestingly, a Spearman's negative association was found between the viral RNA loads quantified by the Quanty assay and the C T values of RT PCRs performed with either the Allplex™ assay or the Simplexa™ assay. However, the strength of this association was higher for the Allplex™ assay (N gene, ρ = - 0.92; RdRP gene, ρ = - 0.91) than for the Simplexa™ assay (ORF1ab gene, ρ = - 0.65; S gene, ρ = - 0.80). The Allplex™ 2019-nCoV, the Simplexa™ COVID-19 Direct, and the Quanty COVID-19 assays yielded comparable results. However, the role these assays might play in future clinical practice warrants larger comparison studies.

We used nasopharyngeal swab samples of patients with a symptomatic (n = 82) or asymptomatic (n = 20) coronavirus disease 2019 (COVID-19) diagnosis to assess the ability of antigen detection tests to infer active (potentially transmissible) or inactive (potentially non-transmissible) infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Using the subgenomic RNA (sgRNA) as an active replication marker of SARS-CoV-2, 48 (76.2%), 56 (88.9%), and 63 (100%) of 63 samples with sgRNA positive results tested positive with the SD BIOSENSOR STANDARD Q COVID-19 Ag (Standard Q), the SD BIOSENSOR STANDARD F COVID-19 Ag FIA (Standard F), or the Fujirebio LUMIPULSE G SARS-CoV-2 Ag (Lumipulse) assay, respectively. Conversely, 37 (94.9%), 29 (74.4%), and 7 (17.9%) of 39 samples with sgRNA negative results tested negative with Standard Q, Standard F, or Lumipulse, respectively. Stratifying results by the number of days of symptoms before testing revealed that most antigen positive/sgRNA positive results were among samples tested at 2–7 days regardless of the assay used. Conversely, most antigen negative/sgRNA negative results were among samples tested at 16–30 days only when Standard Q or Standard F were used. In conclusion, based on our findings, a negative antigen test, especially with the Lumipulse assay, or a positive antigen test, especially with the Standard F assay, may suggest, respectively, the absence or presence of replication-competent SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Background: Since December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as a novel etiologic agent of viral pneumonia. We aimed to compare clinical features of 165 Italian patients with laboratory confirmed or unconfirmed 2019-nCoV pneumonia.Methods: On March 31, 2020, hospitalized patients who presented with fever and/or respiratory symptoms, exposures, and presence of lung imaging features consistent with 2019-nCoV pneumonia were included. Before admission to a hospital ward, patients underwent RT-PCR based SARS-CoV-2 RNA detection in their nasopharyngeal swab samples.Results: Of 165 patients studied, 119 had positive RT-PCR results and 46 were RT-PCR negative for 2 days or longer (i.e., when the last swab sample was obtained). The median age was 70 years (IQR, 58-78), and 123 (74.6%) of 165 patients had at least one comorbidity. The majority of patients (101/165, 61.2%) had a mild pneumonia, and the remaining patients (64/165, 38.8%) a severe/critical pneumonia. We did not find any substantial difference in symptoms, incubation periods, and radiographic/CT abnormalities as well as in many of the biological abnormalities recorded. However, at multivariable analysis, higher concentrations of hemoglobin (OR, 1.34; 95% CI, 1.11-1.65; P = 0.003) and lower counts of leukocytes (OR, 0.81; 95% CI, 0.72-0.90; P < 0.001) were statistically associated with confirmed COVID-19 diagnosis. While mortality rates were similar, patients with confirmed diagnosis were more likely to receive antivirals (95% vs 19.6%, P < 0.001) and to develop ARDS (63% vs 37%, P = 0.003) than those with unconfirmed COVID-19 diagnosis.Conclusions: Our findings suggest that unconfirmed 2019-nCoV pneumonia cases may be actually COVID-19 cases and that clinicians should be cautious when managing patients with presentations compatible with COVID-19. [ABSTRACT FROM AUTHOR]

Coinfections with bacteria or fungi may be a frequent complication of COVID-19, but coinfections with Candida species in COVID-19 patients remain rare. We report the 53-day clinical course of a complicated type-2 diabetes patient diagnosed with COVID-19, who developed bloodstream infections initially due to methicillin-resistant Staphylococcus aureus, secondly due to multidrug-resistant Gram-negative bacteria, and lastly due to a possibly fatal Candida glabrata. The development of FKS-associated pan-echinocandin resistance in the C. glabrata isolated from the patient after 13 days of caspofungin treatment aggravated the situation. The patient died of septic shock shortly before the prospect of receiving potentially effective antifungal therapy. This case emphasizes the importance of early diagnosis and monitoring for antimicrobial drug-resistant coinfections to reduce their unfavorable outcomes in COVID-19 patients. [ABSTRACT FROM AUTHOR]

We analyzed the bacterial communities of the nasopharynx in 40 SARS-CoV-2 infected and uninfected patients. All infected patients had a mild COVID-19 disease. We did not find statistically significant differences in either bacterial richness and diversity or composition. These findings suggest a nasopharyngeal microbiota at least early resilient to SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Objective  To date, no information on late-onset infection in newborns to mother with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contracted in pregnancy are available. This study aimed to evaluate postdischarge SARS-CoV-2 status of newborns to mothers with COVID-19 in pregnancy that, at birth, were negative to SARS-CoV-2. Study Design  This is an observational study of neonates born to mothers with coronavirus disease 2019 (COVID-19). Results  Seven pregnant women with documented SARS-CoV-2 infection have been evaluated in our institution. One woman had a spontaneous abortion at 8 weeks of gestational age, four women recovered and are still in follow-up, and two women delivered. Two newborns were enrolled in the study. At birth and 3 days of life, newborns were negative to SARS-CoV-2. At 2-week follow-up, one newborn tested positive although asymptomatic. Conclusion  Our findings highlight the importance of follow-up of newborns to mothers with COVID-19 in pregnancy, since they remain at risk of contracting the infection in the early period of life and long-term consequences are still unknown. Key Points Newborns to mothers with coronavirus disease 2019 (COVID-19) in pregnancy can acquire the infection later after birth. Newborns to mothers with COVID-19 in pregnancy need a long-term follow-up, even if they tested negative at birth. Specific guidelines for the long-term follow-up of newborns to mothers with COVID-19 in pregnancy are needed. [ABSTRACT FROM AUTHOR]

Background: SARS-CoV-2 antigen detection has currently expanded the testing capacity for COVID-19, which yet relies on the SARS-CoV-2 RNA RT-PCR amplification. Objectives: To report on a COVID-19 testing algorithm from a tertiary care hospital emergency department (ED) that combines both antigen (performed on the ED) and RT-PCR (performed outside the ED) testing. Methods: Between December 2020 and January 2021, in a priori designated, spatially separated COVID-19 or non-COVID-19 ED areas, respectively, symptomatic or asymptomatic patients received SARS-CoV-2 antigen testing on nasopharyngeal swab samples. Antigen results were promptly accessible to guide subsequent, outside performed confirmatory (RT-PCR) testing. Results: Overall, 1083 (100%) of 1083 samples in the COVID-19 area and 1815 (49.4%) of 3670 samples in the non-COVID-19 area had antigen results that required confirmation by RT-PCR. Antigen positivity rates were 12.4% (134/1083) and 3.7% (66/1815), respectively. Compared to RT-PCR testing results, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of antigen testing were, respectively, 68.0%, 98.3%, 88.8%, and 94.1% in the COVID-19 area, and 41.9%, 97.3%, 27.3%, and 98.6% in non-COVID-19 area. Practically, RT-PCR tests were avoided in 50.6% (1855/3670) of non-COVID-19 area samples (all antigen negative) from patients who, otherwise, would have needed antigen result confirmation. Conclusions: Our algorithm had value to preserve RT-PCR from avoidable usage and, importantly, to save time, which translated into a timely RT-PCR result availability in the COVID-19 area. [ABSTRACT FROM AUTHOR]

Diagnostic methods based on SARS-CoV-2 antigens detection are a promising alternative to SARS-CoV-2 RNA amplification. We evaluated the automated chemiluminescence-based Lumipulse® G SARS-CoV-2 Ag assay on saliva samples, using Simplexa™ COVID-19 Direct assay as a reference test. Analytical performance was established on a pool of healthy donors' saliva samples spiked with the 2019-nCoV/Italy-INMI1 isolate, whereas clinical performance was assessed on fresh saliva specimens collected from hospitalized patients with suspect or confirmed COVID-19 diagnosis. The limit of detection (LOD) was 0.65 Log TCID50/mL, corresponding to 18,197 copies/mL of SARS-CoV-2 RNA. Antigen concentrations and SARS-CoV-2 RNA were highly correlated (r = 0.99; p < 0.0001). Substantial agreement (80.3%) and significant correlation (r = −0.675; p = 0.0006) were observed between Lumipulse® G assay results and Ct values on clinical samples, with 52.4% sensitivity and specificity 94.1%. Sensitivity exceeded 90.0% when calculated on samples with Ct < 25, and specificity was 100% when excluding samples from recovered patients with previous COVID-19 diagnosis. Overall, chemiluminescence-based antigen assay may be reliably applied to saliva samples to identify individuals with high viral loads, more likely to transmit the virus. However, the low positive predictive value in a context of low SARS-CoV-2 prevalence underscores the need for confirmatory testing in SARS-CoV-2 antigen-positive cases. [ABSTRACT FROM AUTHOR]

This would be consistent with the viral load kinetics within the first days of SARS-CoV-2 infection, showing that nasopharynx swab samples obtained on day 7 may be persistently positive (Ct values, 23-24) for SARS-CoV-2 [[5]]. To the Editor, Among the laboratory testing methods developed for identifying patients with acute infection due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) - the aetiological agent of coronavirus disease 2019 (COVID-19) - viral RNA amplification using real-time PCR (RT-PCR) is to date the standard method in many clinical virology laboratories [[1]]. According to RT-PCR Ct values, the sample per cent positivity of the STANDARD F COVID-19 Ag FIA ranged from 100.0% (5/5; Ct, <18), 93.8% (15/16; Ct, >=18-<25), 42.0% (23/55; Ct, >=25-<35) to 21.0% (6/28; Ct, >=35). [Extracted from the article]