Effectiveness of Rapid Antigen Testing in Forensic Cases of Severe Acute Respiratory Syndrome Coronavirus 2 Infection, Including Delta Variant

Abstract

The polymerase chain reaction is indispensable for diagnosing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in forensic cases. However, studies regarding the effectiveness of rapid antigen testing (RAT) in forensic cases remain limited. Therefore, we investigated the efficacy of RAT compared with reverse–transcription quantitative polymerase chain reaction (RT-qPCR) for confirming SARS-CoV-2 infection (including the delta variant). Before the external examination or autopsy, we collected samples from the nasopharyngeal mucosa, which were then assessed via RAT (QuickNavi COVID-19 Ag kit, QuickNavi-Flu+COVID-19 Ag kit) and RT-qPCR. Reverse-transcription quantitative polymerase chain reaction results were positive in 73 of 1255 cases, and 21 cases were identified as those of delta variants. Low RT-qPCR threshold cycle value cases and delta variant infections were more likely to result in coronavirus disease-related deaths. The sensitivity of the QuickNavi COVID-19 Ag kit was 76.32%, and that of the QuickNavi-Flu+COVID-19 Ag kit was 77.14%. The specificity of both RATs was 100%. In QuickNavi COVID-19 Ag kit cases, delta variant cases showed lower sensitivity than non-delta variant cases, even for a similar viral load. Thus, RAT in forensic cases is sufficiently useful as a screening test for SARS-CoV-2 infection. However, RAT carries a risk of false negatives, especially for delta variant cases.