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Assessment of commercial severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) immunoassays for their capacity to provide reliable information on sera neutralizing activity is an emerging need. We evaluated the performance of two commercially available lateral flow immunochromatographic assays (LFIC; Wondfo SARS‐CoV‐2 Antibody test and the INNOVITA 2019‐nCoV Ab test) in comparison with a SARS‐CoV‐2 neutralization pseudotyped assay for coronavirus disease 2019 (COVID‐19) diagnosis in hospitalized patients and investigate whether the intensity of the test band in LFIC associates with neutralizing antibody (NtAb) titers. Ninety sera were included from 51 patients with moderate to severe COVID‐19. A green fluorescent protein (GFP) reporter‐based pseudotyped neutralization assay (vesicular stomatitis virus coated with SARS‐CoV‐2 spike protein) was used. Test line intensity was scored using a 4‐level scale (0 to 3+). The overall sensitivity of LFIC assays was 91.1% for the Wondfo SARS‐CoV‐2 Antibody test, 72.2% for the INNOVITA 2019‐nCoV IgG, 85.6% for the INNOVITA 2019‐nCoV IgM, and 92.2% for the NtAb assay. Sensitivity increased for all assays in sera collected beyond day 14 after symptoms onset (93.9%, 79.6%, 93.9%, and 93.9%, respectively). Reactivities equal to or more intense than the positive control line (≥2+) in the Wondfo assay had a negative predictive value of 100% and a positive predictive value of 96.4% for high NtAb50 titers (≥1/160). Our findings support the use of LFIC assays evaluated herein, particularly the Wondfo test, for COVID‐19 diagnosis. We also find evidence that these rapid immunoassays can be used to predict high SARS‐CoV‐2‐S NtAb50 titers. [ABSTRACT FROM AUTHOR]

Knowledge of the precise timing of SARS‐CoV‐2 infection may be of clinical and epidemiological relevance. The presence of low‐avidity IgGs has conventionally been considered an indicator of recent infection. Here, we carried out qualitative assessment of SARS‐CoV‐2‐specific antibody avidity using an urea (6M) dissociation test performed on a lateral flow immunochromatographic IgG/IgM device. We included a total of 76 serum specimens collected from 57 COVID‐19 patients, of which 39 tested positive for both IgG and IgM and 37 only for IgG. Sera losing IgG reactivity after urea treatment (n = 28) were drawn significantly earlier (P =.04) after onset of symptoms than those which preserved it (n = 48). This assay may be helpful to estimate the time of acquisition of infection in patients with mild to severe COVID‐19. Highlights: A LFIC test was adapted for assessing SARS‐CoV‐2 antibody avidity. This urea dissociation LFIC assay may hep to determine the time of SARS‐CoV‐2 infection. [ABSTRACT FROM AUTHOR]

Caveats in interpreting SARS-CoV-2 IgM+/IgG- antibody profile in asymptomatic health care workers Serological testing is increasingly recognized as a useful tool for management of the coronavirus disease-2019 (COVID-19) pandemic.1 Cross-sectional serosurveys provide information on exposure levels in a target population, which is helpful for designing public health strategies to blunt community transmission.2 To maximize sensitivity, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence could be defined as positivity of any antibody isotype (IgG, IgM, or IgA), as detected by enzyme-linked immunosorbent assays or chemiluminescent immunoassays (CLIA).3-5 Theoretically, however, this approach may lead to false-positive results outnumbering true-positive ones in low prevalence settings, even when highly specific assays are used. Qualitative assessment of SARS-CoV-2-specific antibody avidity by lateral flow immunochromatographic IgG/IgM antibody assay. [Extracted from the article]

Amplification of human -glucuronidase gene for appraising the accuracy of negative SARS-CoV-2 RT-PCR results in upper respiratory tract specimens Real-time reverse transcription polymerase chain reaction (RT-PCR) is the mainstay of coronavirus disease 2019 (Covid-19) diagnosis.1 Up to 30% of the patients clinically suspected of Covid-19 may have initial or repeat RT-PCR negative results before positive test conversion, most notably when upper respiratory tract (URT) specimens are processed.2-7 False-negative RT-PCR results may hamper the clinical management of patients and hinder the adoption of epidemiological measures to control the pandemic. A total of 47 URT specimens from 21 patients testing positive by RT-PCR in the second or third specimen were subjected to GUSB gene RT-PCR analysis, which was performed in a parallel to viral RT-PCR testing. [Extracted from the article]