Sample and Data Analysis
Seventy-five (75) frozen archived nasopharyngeal samples – consisting of 38 positive and 37 negative rRT- PCR tested COVID-19 samples were obtained for the evaluation of the three (3) brands of the immunochromatographic RDT kits. The archived samples were selected using a flow chart (supplementary figure 1, SF1 ). It is worth noting that these samples were retested using rRT-PCR (the reference test, S0 ) prior to the immunochromatographic assays (the index test, S1 ). The three immunochromatographic antigen kits (i.e., DG Rapid, SD Rapid, and SS Rapid) consist of qualitative membrane-based immunoassays and detect SARS-CoV-2 nucleocapsid antigen. All assays were performed by a single operator for each brand of test kit, with two blind operators reading the results. In case of discrepancies, a third operator was consulted, especially for faint test lines. All tests were performed according to the manufacturer’s instructions (10–12). The results generated were entered into Microsoft Excel-365 and analyzed using IBM SPSS Statistics version 23. A Flow chart of the method from sample selection to data analysis can be found in supplementary figure 1 (SF1)
Results