Comparação entre teste imunocromatográfico e molecular para detecção do SARS-CoV-2

Abstract

COVID-19 is an infectious disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The disease, highly transmissible and contagious, has a variable clinical spectrum. Laboratory diagnosis is based on molecular tests, such as qRT-PCR, and serological tests, such as those designed to detect specific antibodies (IgM and/or IgG) or viral antigens. SARS-CoV-2 has the ability to adapt to human hosts through the development of mutations, which can be accumulated, resulting in variants of the virus. Several factors have been identified as possible interferents in the performance of rapid antigen tests (RATs), such as the type of sample, stage of infection, viral load, symptomatology, sample quality, storage and transport conditions, as well as the different variants. In this study, sociodemographic, epidemiological and laboratory analyses were conducted to evaluate the influence of factors that can affect the performance of RATs, through a comparison between the results obtained through testing 180 nasopharyngeal swab samples, selected from different periods, using the RAT methods in relation to RT-qPCR. For this purpose, the sensitivity and specificity rates were estimated, in order to compare and verify the divergences in the performance of the RAT in periods when different variants of the virus were in higher circulation in Brazil, correlating with the symptomatology and viral load of the samples. The RT-qPCR results were used as a standard to determine the true-positive samples for the disease. The overall sensitivity (total cohort) was 69.6% (95% confidence interval [CI] = 47.1% to 86.8%) in 2020); 34.4% (95% CI = 18.6% to 53.2%) in 2021 and 57.1% (95% CI = 39.4% to 73.7%) in 2022. Therefore, heterogeneity was observed in the estimated sensitivity between the symptomatic and asymptomatic groups for the variants studied. Evaluating the sensitivity rate for different viral loads resulted in an apparent reduction in sensitivity, especially for Ct values > 25 (low viral load), ranging from 44.0% to 14.0% for samples detected in 2021 and 33.0% to 29.0% for samples detected in 2022. By contrast, for Ct < 25 (high viral load), the sensitivity rates were 100%. Specificity was maintained at 100%. Thus, viral load was considered a highly relevant factor in determining the performance of the SARS-CoV-2 antigen test. Thus, despite the heterogeneity in the RAT sensitivity rates, it is possible to state that the test was able to accurately detect all the samples detected during the selected periods, by respecting the previously existing and highly widespread recommendations in the literature (Ct < 25, Until the 7th day of symptoms, approximately). Furthermore, continuous monitoring of the analytical performance of these devices is recommended in order to guarantee diagnostic quality in the detection of the virus.