Evaluation of rapid, cassette immunochromatographic tests in the serological diagnosis of COVID-19

Introduction: Lateral flow assays (LFIA) are the technology behind low-cost, simple, rapid and portable detection devices popular in biomedicine. Lately, they are very common used in serodiagnosis of SARS-CoV-2 infections. The aim of the presented study was to assess the usefulness of selected LFIA in serological diagnosis of COVID-19. Methods: The usefulness of seven lateral flow assays in the serodiagnosis of COVID-19 was evaluated (VAZYME, DIAGNOSIS, PCL, INGEZIM, BIOSENSOR, ACCU-TELL, NOVAtest). The study used 107 serum samples obtained from 74 individuals with current SARS-CoV-2 infection confirmed by RT-PCR. The ELISA-IgG (Euroimmun) was used as the reference assay for sensitivity and specificity testing. Results: The highest percentage of positive results was obtained when searching for IgG antibodies with the NOVAtest (40.6%) and DIAGNOSIS (39.2%) sets and the lowest detection for the PCL set - 25.5%. In the case of searching for IgM antibodies in all sets, significantly lower percentages of positive results compared to the IgG class were recorded. In general, all lateral flow assays showed low sensitivity in relation to the Euroimmun ELISA-IgG. The DIAGNOSIS kit (64.5%) was characterized by the highest sensitivity, and the PCL kit was the lowest (38.7%). On the other hand, the specificity of all kits was very high, almost 100% in almost all cases. Conclusions: Lateral flow assays due to their low sensitivity are not suitable for quick diagnosis of the current SARS-CoV-2 infections and cannot be an alternative to genetic or even antigen tests. They may be used only to retrospectively test the presence of IgG antibodies. However, a negative results of LFIA in suspected disease or after vaccination should be confirmed by more sensitive serological tests.