In our study, FebriDx MxA had a high negative predictive value for COVID-19 (96%; 95% CI, 94%–97%) compared with the reference standard of PCR, which is highly consistent with findings in our previously published diagnostic accuracy study.11 This high negative predictive value, despite the high prevalence of SARS-CoV-2 in this study, enables confident decision making in ED, allowing FebriDx MxA-negative patients to be rapidly moved from high-risk to lower-risk areas without waiting for the results of PCR testing. Here, MX1 is linked to COVID-19.