Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), has spread rapidly around the globe since it was first identified in December of 2019 in Wuhan, China. In a race to contain the infection, researchers and healthcare officials have developed several assays to help diagnose individuals with COVID-19. To help laboratories decide what assay to bring into testing lines, factors such as assay availability, cost, throughput, and TAT should be considered. ⋯ A deeper look at the Ct values showed no significant difference between NeuMoDx and the modified CDC SARS-CoV-2 assay, whereas DiaSorin had lower overall Ct values than the modified CDC SARS-CoV-2 assay. NeuMoDx and DiaSorin workflows were much easier to perform. NeuMoDx has the highest throughput and shortest TAT, whereas although the modified CDC SARS-CoV-2 assay has comparable throughput to DiaSorin, it has the longest hands-on time and highest TAT.
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Antibody testing has recently emerged as an option to assist with determining exposure to SARS-CoV-2, the causative agent of COVID-19. Elucidation of the kinetics and duration of the humoral response is important for clinical management and interpreting results from serological surveys. ⋯ This study demonstrates the Abbott IgM assay against SARS-CoV-2 is detected slightly earlier compared to IgG, with both tests exhibiting excellent overall sensitivity and specificity. In symptomatic patients who test negative by PCR for a SARS-CoV-2 infection, assessing IgM and IgG antibodies can aid in supporting a diagnosis of COVID-19.
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The clinical significance of high crossing threshold (Ct) detection of SARS-CoV-2 by RT-PCR is inadequately defined. In the course of universal admission screening with the Cepheid Xpert Xpress SARS-CoV-2 assay at our institution, we observed that 3.9 % (44/1123) of SARS-CoV-2 positive results were negative for the envelope (E) gene target but positive for the nucleocapsid (N2) target. The overall SARS-CoV-2 positivity rate during the three-month study period was 15.4 % (1123/7285), spanning April-June 2020. ⋯ Critically, E-negative, N2-positive results were observed in 8 symptomatic patients with a new diagnosis of COVID-19. Thus, though concerns remain about extended SARS-CoV-2 RT-PCR positivity in some patients, the ability of clinical laboratories to detect patients with high Ct values (including E-negative, N2-positive results) is vital for retaining maximal sensitivity for diagnostic purposes. Our data show that a finding of E-positive, N2-negative SARS-CoV-2 should not be used to rule out the presence of subclinical infection.
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Comparative Study
Analytical sensitivity and clinical sensitivity of the three rapid antigen detection kits for detection of SARS-CoV-2 virus.
Numerous rapid antigen detection (RAD) kits for diagnosing COVID-19 patients are available in the market recently. ⋯ Although RAD kits were less sensitive than RT-PCR, understanding the clinical characteristics of different RAD kits can guide us to obtain suitable specimens for testing. The likelihood of positive results for RAD kits will be higher.
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The aim of the present study was to evaluate the clinical performance of four SARS-CoV-2 immunoassays and their contribution in routine care for the diagnosis of COVID-19, in order to benefit of robust data before their extensive use. ⋯ Serology was complementary to RT-PCR for the diagnosis of COVID-19 at least 14 days after onset of symptoms. First line serology testing can be performed with Wantai Ab or Abbott IgG assays, while DiaPro IgG confirmation assay can be used as an efficient confirmation assay.