For the in-house nucleocapsid IgG ELISA, four samples that were repeatedly false positive samples turned negative when nucleocapsid was added. using 300 pre-epidemic samples and 100 PCR-confirmed COVID-19 samples. The sensitivities and specificities of the assays were as follows: 90%/100% (in-house trimer spike IgA), 90%/99.3% (in-house trimer spike IgG), 89%/98.3% (in-house nucleocapsid IgG), 73.7%/100% (EDI nucleocapsid IgM), 84.5%/95.1% (EDI nucleocapsid IgG), 95%/93.7% (Euroimmun S1 IgA), 82.8%/99.7% (Euroimmun S1 IgG), 82.0%/91.7% (Chembio nucleocapsid IgM), 92%/93.3% (Chembio nucleocapsid IgG). The presumed causes of false positive results from pre-epidemic samples in commercial and in-house assays were mixed. In some cases, assays lacked reproducibility. In other cases, reactivity was abrogated by competitive inhibition (spiking the sample with the same antigen that was used for coating ELISAs prior to performing the AGN 194310 assay), suggesting positive reaction could be attributed to the presence of antibodies against these antigens. In other cases, reactivity was consistently detected but not abrogated by the spiking, suggesting positive reaction was not attributed to the presence of antibodies against these antigens. Overall, there was wide variability in assay performance using our samples, with in-house tests exhibiting the highest combined sensitivity and specificity. The causes of false positivity in pre-epidemic samples may be due to plasma antibodies apparently reacting with the corresponding antigen, or spurious reactivity may be directed against non-specific components in the assay system. Identification of these targets will be essential to improving assay performance. Introduction There is an urgent need for an accurate serologic test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Antigen and antibody detection methods play important roles in disease management and control of COVID-19. AGN 194310 Due to the high specificity of the reverse transcriptase Real Time MADH9 PCR (rRT-PCR) for detecting the presence of the virus during the acute phase , it is considered the gold standard for COVID-19 clinical testing . Antibody testing currently plays a limited role in testing patients , due to the potentially long window period of 1 to 2 2 weeks after onset of symptoms [4,5]; however, they can be critical in other aspects of the disease. Antibody based tests can be used for detection of previously infected patients for population-level surveillance, as a confirmatory assay for PCR testing, as a cost-effective method for primary diagnostic test in low-income settings, defining the antibody titers following vaccination, screening eligible convalescent plasma donors, and potentially determining protection against re-infection . Among the four major structural proteins encoded by SARS-CoV-2 genome, i.e spike (S), envelope (E), membrane (M), and nucleocapsid (N) , AGN 194310 the two latter proteins are highly immunogenic and therefore are widely used in serologic assays . At the time of writing this paper, the U.S. Food and Drug Administration (FDA) has authorized 51 antibody tests under Emergency Use Authorization (EUA) . However, because of the long time to seroconversion, as well as lack of specificity, the CDC currently only recommends serologic testing in certain clinical situations, such as presentation after 9 days of illness onset, and those presenting with late complications of COVID-19 . Despite their importance in disease management, the performance of many commercially available SARS-CoV-2 serologic tests have not been fully evaluated with large panels of samples, thus, their utility is questionable . A number of these tests have been recalled due to poor performance. Because seasonal coronaviruses have conceivably infected the majority of the human population, cross reactivity to the common coronaviruses is an important concern in developing SARS-CoV- 2 serology tests. These AGN 194310 tests include ELISA, and chemiluminescent microparticle immunoassay.
For the in-house nucleocapsid IgG ELISA, four samples that were repeatedly false positive samples turned negative when nucleocapsid was added
- by globalhealth