Diagnostic performance of LumiraDx SARS-CoV-2 rapid antigen test compared to PCR for diagnosis of COVID-19 in Liberia

Background Diagnosis of SARS-CoV-2 infection in Liberia has primarily relied on polymerase chain reaction (PCR)-based testing at the country’s National Reference Laboratory. This centralized approach caused reporting delays, prompting evaluation of point-of-care antigen-based tests. We assessed the test performance of the LumiraDx™ SARS-CoV-2 Ag test (LumiraDx™, London, UK) in this setting. Methods We tested ambulatory individuals screened for enrollment into an observational cohort study of COVID-19 sequelae in Monrovia in 2021. We compared the results of LumiraDx testing of anterior nasal swab specimens to the results of PCR BioFire® R2.1P (bioMérieux, Salt Lake City, Utah) on eluent from nasopharyngeal swabs. Results We evaluated 348 individuals. Among the 274 persons with symptoms, 49.3% were PCR-positive and 36.5% were antigen-positive. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of LumiraDx in this group were 72.6% (95% CI: 64.3%-79.9%), 98.6% (95% CI: 94.9%-99.8%), 78.7% (CI: 71.9%-84.6%), and 98.0% (CI: 93.0%-99.8%), respectively. Among the 74 asymptomatic individuals, 12.2% were positive by PCR, and 5.5% by antigen testing, resulting in a sensitivity, specificity, NPV, and PPV of LumiraDx of 44.4% (95% CI: 13.7%-78.8%), 100% (95% CI: 94.5%-100%), 92.9% (CI: 84.1%-97.6%), and 100% (CI: 39.8%-100%), respectively. Conclusion Although the specificity and PPV of LumiraDx for diagnosing SARS-CoV-2 were high among persons with and without symptoms, the sensitivity was unacceptably low in both groups, and much less than that reported by the manufacturer. Before new point-of-care diagnostics are adopted, test performance needs to be assessed in the local setting. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was supported by the U.S. National Institutes of Health/National Institute of Allergy and Infectious Disease (NIH/NIAID), Partnership for Research on Ebola Virus in Liberia (PREVAIL); the Fogarty International Center/NIAID (U2R TW011281); and the U.S. National Institute of Mental Health/NIH (R25 MH123256). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The National Research Ethics Board of Liberia I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors