ABSTRACT
Background: An accessible and sensitive and sensitive method for determining antibodies to a new coronavirus infection is often the key to timely provision of the necessary medical care to patients with rheumatic diseases Objectives: Compare methods for determining antibodies to SARS-CoV-2 using a rapid test and enzyme-linked immunosorbent assay (ELISA) Methods: Methods for determining antibodies to SARS-CoV-2 using an express test (Chromatographic express test SARS-CoV-2 IgG / IgM (Xiamen Biotime Biotechnology, China)) and by ELISA (Reagent kit for enzyme immunoassay of class G immunoglobulins and class M to SARS-CoV-2 (Vector-Best, Russia)) were compared. 80 patients were included with a diagnosis of rheumatoid arthritis 26 (33%), psoriatic arthritis -9 (11%), osteoarthritis -15 (19%), rheumatic heart disease 1 (1%), SLE 2 (3%), deramtomyositis 3 (4%), systemic sclerosis 5 (6%), systemic connective tissue diseases 4 (5%), including Sjogren's syndrome, spondyloarthritis 15 (19%). 17 (21%) denied a history of COVID-19 symptoms. 63 (79%) noted any signs of COVID-19 3.095 ± 1.45 months before the test (Median 3 [2;4] months). 63 (79%) noted any signs of COVID-19 109 ± 43 days before the test (Median 111 [78;135] months). The ELISA method was considered the standard. Results: When comparing the results of the express test and the determination of IgG antibodies to SARS-CoV-2 in serum, the following was obtained: the sensitivity of the express test is 99%. When comparing the results of the express test and the determination of IgM antibodies to SARS-CoV-2 in serum, it was obtained: among 66 samples with a negative result by the express test method, IgM was detected in 6 cases by ELISA/ So, 7.5% of 80 samples were false negative. In 3 of 14 samples with a positive result by the express test, IgM by ELISA was not detected. So, 3.75% of 80 samples were false-positive. (Table 1). When comparing the results of the IgM express test and ELISA, the following was obtained: the sensitivity of the express test was 33%, the specificity was 85%.Conclusion: When comparing the results of the express test and the determination of IgG antibodies to SARS-CoV-2 in serum, the sensitivity of the express test is 99%. Determination of IgM antibodies to SARS-CoV-2 using a rapid test is less reliable than determination using ELISA.