Recent Advances in the Evaluation of Serological Assays for the Diagnosis of SARS-CoV-2 Infection and COVID-19

Abstract

Introduction: Few data on the diagnostic performance of serological tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are currently available. We evaluated sensitivity and specificity of five different widely used commercial serological assays for the detection of SARS-CoV-2–specific IgG, IgM, and IgA antibodies using reverse transcriptase-PCR assay in nasopharyngeal swab as reference standard test.Methods: A total of 337 plasma samples collected in the period April–June 2020 from SARS-CoV-2 RT-PCR positive (n = 207) and negative (n = 130) subjects were investigated by one point-of-care lateral flow immunochromatographic assay (LFIA IgG and IgM, Technogenetics) and four fully automated assays: two chemiluminescence immunoassays (CLIA-iFlash IgG and IgM, Shenzhen YHLO Biotech and CLIA-LIAISON® XL IgG, DiaSorin), one electrochemiluminescence immunoassay (ECLIA-Elecsys® total predominant IgG, Roche), and one enzyme-linked immunosorbent assay (ELISA IgA, Euroimmune).Results: The overall sensitivity of all IgG serological assays was >80% and the specificity was >97%. The sensitivity of IgG assays was lower within 2 weeks from the onset of symptoms ranging from 70.8 to 80%. The LFIA and CLIA-iFlash IgM showed an overall low sensitivity of 47.6 and 54.6%, while the specificity was 98.5 and 96.2%, respectively. The ELISA IgA yielded a sensitivity of 84.3% and specificity of 81.7%. However, the ELISA IgA result was indeterminate in 11.7% of cases.Conclusions: IgG serological assays seem to be a reliable tool for the retrospective diagnosis of SARS-CoV-2 infection. IgM assays seem to have a low sensitivity and IgA assay is limited by a substantial rate of indeterminate results.

COVID-19 Antibody Detecting Rapid Diagnostic Tests Show High Cross-Reactivity When Challenged with Pre-Pandemic Malaria, Schistosomiasis and Dengue Samples

“…However, five RDT products explicitly prescribed to consider any shade of color as a positive reading. In addition, low intensity has been reported frequently among true-positive test lines in COVID-19 RDTs assessed in independent evaluation studies or deployed in seroprevalence studies in Europe [ 14 , 54 , 55 , 56 , 57 , 58 , 59 ]; in the latter studies, proportions of low intensity were comparable to the present cross-reactive line intensities [ 58 , 59 ]. In the case of seroprevalence studies, this may partly be explained by lower antibody levels in non-symptomatic individuals [ 60 ].…”

Dynamics of spike-and nucleocapsid specific immunity during long-term follow-up and vaccination of SARS-CoV-2 convalescents

“…We identified 108 individuals who tested positive for anti-SARS-CoV-2 IgG by an indirect chemiluminescence immunoassay (iFlash CLIA, YHLO Biotechnology, China; specificity 99.3% (98.3–99.7), sensitivity 94% (89.0–96.8)) 92 , 93 , among whom 94 individuals agreed to participate in the follow-up study. Among these, positive anti-SARS-CoV-2 IgG testing was confirmed in 89 participants by at least two further commercial assay systems, and in one further assay system in two individuals, for which material was limited, resulting in a combined specificity of at least 99.94%.…”

Persistence of functional memory B cells recognizing SARS-CoV-2 variants despite loss of specific IgG

“…Because the consequences of infection with SARS-CoV-2 range from asymptomatic to lethal, accurate confirmation of previous infections is of great epidemiological and prognostic significance. Serological testing has made great advances (Chiereghin et al, 2020;Galipeau et al, 2020;Huang et al, 2020;Zarletti et al, 2020), but the specific IgG response wanes over time, and some donors with previous infections score negative in current serology tests (Abayasingam et al, 2021;Dan et al, 2021). We showed that the donors who lost IgG to SARS-CoV-2 still had specific IgG memory B cells.…”