Rapid antigen tests for positive Covid-19 confirmation in the laboratory setting

Abstract

Introduction: Pooling patient samples for PCR testing increases throughput and has become standard practice during the COVID-19 pandemic. Accurate, rapid and cost-effective methods to determine the actual positive sample from a pooled well are needed. Aims: To determine the utility of rapid antigen tests for discerning the positive COVID-19 sample from pooled test results that are positive. Methods: 15 known positive and negative Covid-19 samples were tested using the Abbott Panbio COVID-19 Ag Rapid test device with a modified method suitable for use in the laboratory. Briefly, 150 μL of reaction buffer was mixed with 150 μL of patient sample from liquid swabs and the result was read at 15 minutes. Discussion: The performance of rapid antigen kits in this study were consistent with results using the standard method with direct inoculation of swabs.1 Samples yielding a Ct value below 25 were detected successfully, and those above that threshold failed. Thus for pooled positive results with a Ct value below 25, the current method can be used to discern the positive sample in that pool. This method would also lower the cost of further testing on pooled samples and expedite determination of the positive sample. Data collection is ongoing to further assess. Reference 1. Dinnes J, Deeks JJ, Berhane S, et al. Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection. Cochrane Database Syst Rev 2021; 3: CD013705.