Diagnostic Properties of Three SARS-CoV-2 Antibody Tests

• Main Authors: Suelen Basgalupp, Giovana dos Santos, Marina Bessel, Lara Garcia, Ana Carolina de Moura, Ana Carolina Rocha, Emerson Brito, Giovana de Miranda, Thayane Dornelles, William Dartora, Lucia Pellanda, Pedro Hallal, Eliana Wendland
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Diagnostics
• Subjects: SARS-CoV-2; COVID-19; serological tests; antibodies; point-of-care test; ELISA
• Online Access: https://www.mdpi.com/2075-4418/11/8/1441

Serological assays emerged as complementary tools to RT-PCR in the diagnosis of SARS-CoV-2 as well as being needed for epidemiological studies. This study aimed to assess the performance of a rapid test (RT) compared to that of serological tests using finger prick blood samples. A total of 183 samples were evaluated, 88 of which were collected from individuals with negative RT-PCR and 95 from positive RT-PCR individuals. The diagnostic performance of RT (WONDFO^®) and LUMIT (PROMEGA^®) were compared to that of ELISA (EUROIMMUN^®) for detecting antibodies against SARS-CoV-2 according to time from symptoms onset. The IgG antibody tests were detected in 77.4% (LUMIT), 77.9% (RT), and 80.0% (ELISA) of individuals. The detection of antibodies against SARS-CoV-2 increases in accordance with increasing time from symptoms onset. Considering only time from symptoms onset >21 days, the positivity rate ranged from 81.8 to 97.0% between the three tests. The RT and LUMIT showed high agreement with ELISA (agreement = 91.5%, k = 0.83, and agreement = 96.3%, k = 0.9, respectively) in individuals who had symptoms 15 to 21 days before sample collection. Compared to that of the ELISA assay, our results show sensitivity ranged from 95% to 100% for IgG antibody detection in individuals with symptoms onset between 15 and 21 days before sample collection. The specificity was 100% in individuals with symptoms onset >15 days before serological tests. This study shows good performance and high level of agreement of three immunoassays for the detection of SARS-CoV-2 antibodies.