Comparative analysis of three point-of-care lateral flow immunoassays for detection of anti-SARS-CoV-2 antibodies: data from 100 healthcare workers in Brazil

Abstract

Since the Coronavirus Disease 2019 (COVID-19) pandemic, Brazil has the third-highest number of confirmed cases and the second-highest number of recovered patients. SARS-CoV-2 detection by real-time RT-PCR is the gold standard in certified infrastructured laboratories. However, for large-scale testing, diagnostics should be fast, cost-effective, widely available, and deployed for the community, such as serological tests based on lateral flow immunoassay (LFIA) for IgM/IgG detection. We evaluated three different commercial point-of-care (POC) LFIAs for anti-SARS-CoV-2 IgM and IgG detection in capillary whole blood of 100 healthcare workers (HCW) previously tested by RT-PCR: 1) COVID-19 IgG/IgM BIO (Bioclin, Brazil), 2) Diagnostic kit for IgM/IgG Antibody to Coronavirus (SARS-CoV-2) (Livzon, China); and 3) SARS-CoV-2 Antibody Test (Wondfo, China). A total of 84 positives and 16 negatives HCW were tested. The data was also analyzed by the number of days post symptoms (DPS) in three groups: <30 (n=26), 30-59 (n=42), and >59 (n=16). Overall detection was 85.71%, 47.62%, and 44.05% for Bioclin, Livzon, and Wondfo, respectively, with a specificity of 100%, and 98.75% for Livzon on storage serum samples. Bioclin was more sensitive (p<0.01), regardless of the DPS. Thus, the Bioclin can be used as a POC test to monitor SARS-CoV-2 seroconversion in HCW.

Performance evaluation of a Sars-CoV-2 rapid test and two automated immunoassays

“…A better sensitivity for serum samples with WRT was reported by Cota et al (2020) (18) in a Brazilian study accessing the performance of 12 serological tests for Covid-19 diagnosis, that described an overall sensitivity for Wondfo at 71.7% (64.3%-78.2%). In another evaluation of the Wondfo, Conte et al (2021) (19) have shown a sensibility of 47.6% (37.2%-58.1%) in capillary whole blood. However, it is important to note that the WRT may have a lower sensitivity when used with capillary blood.…”

“…The two samples of positive control group, when evaluated in CMIA-IgM and WRT (IgM/IgG) were positive, however ECLIA, for total antibodies, did not detect the presence of the immunoglobulins in these samples in the initial stage of the disease. In patients with Covid-19, the production of IgM and IgG can be simultaneous and reach in some patients a plateau level after six days (initial stage of the disease) (19) . And about the negative control group sample, there was the presence of cross-reactive antibodies in the ECLIA.…”