Comparative evaluation of six immunoassays for the detection of antibodies against SARS-CoV-2

Objectives: Serologic techniques can serve as a complement to diagnose SARS-CoV-2 infection. The objective of our study was to compare the diagnostic performance of six immunoassays to detect antibodies against SARS-CoV-2: three lateral flow immunoassays (LFAs), one ELISA and two chemiluminescence assays (CLIAs). Methods: We evaluated three LFAs (Alltest, One Step and SeroFlash), one ELISA (Dia.Pro) and two CLIAs (Elecsys and COV2T). To assess the specificity, 60 pre-pandemic sera were used. To evaluate the sensitivity, we used 80 serum samples from patients with positive PCR for SARS-CoV-2. Agreement between techniques was evaluated using the kappa score (k). Results: All immunoassays showed a specificity of 100% except for SeroFlash (96.7%). Overall sensitivity was 61.3%, 73.8%, 67.5%, 85.9%, 88.0% and 92.0% for Alltest, One Step, SeroFlash, Dia.Pro, Elecsys and COV2T, respectively. Sensitivity increased throughout the first two weeks from the onset of symptoms, reaching sensitivities over 85% from 14 days for all LFAs, being One Step the most sensitive (97.6%), followed by SeroFlash (95.1%). Dia.Pro, Elecsys and COV2T showed sensitivities over 97% from 14 days, being 100% for COV2T. One Step showed the best agreement results among LFAs, showing excellent agreement with Dia.Pro (agreement=94.2%, k=0.884), COV2T (99.1%, k=0.981) and Elecsys (97.3%, k=0.943). Dia.Pro, COV2T and Elecsys also showed excellent agreement between them. Conclusions: One Step, Dia.Pro, Elecsys and COV2T obtained the best diagnostic performance results. All these techniques showed a specificity of 100% and sensitivities over 97% from 14 days after the onset of symptoms, as well as excellent levels of agreement.