Field evaluation of COVID‐19 antigen tests versus RNA based detection: Potential lower sensitivity compensated by immediate results, technical simplicity, and low cost

One year into the coronavirus disease 2019 (COVID‐19) pandemic, diagnostic strategies, although central for contact tracing and other preventive measures, are still limited. To meet the global demand, lower cost and faster antigen tests for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) detection are a convenient alternative to the gold standard reverse transcription‐polymerase chain reaction (RT‐PCR) assay. We tested laboratory‐based RT‐PCR RNA detection and two rapid antigen detection (RAD) tests, based on the immunochromatography test for nucleocapsid protein of SARS‐CoV‐2 (COVID‐19 Ag ECO Test, ECO Diagnóstica, and Panbio COVID‐19 Ag Rapid Test Abbott). Paired collection and testing were done in a small prospective open study in three clinical services in São Paulo, constituted of mostly symptomatic volunteers at collection (97%, 109/112) for a median of 4 days (interquartile range: 3–6), ranging from 1 to 30. Among the 108 paired RT‐PCR/RAD tests, results were concordant in 96.4% (101/108). The test's performance was comparable, with an overall sensitivity of 87% and a specificity of 96%. These observations add to other data that suggest that antigen tests may provide reasonable sensitivity and specificity and deserve a role to improve testing strategies, especially in resource‐limited settings. Research Highlights Testing and isolating individuals transmitting SARS‐CoV‐2, generally with high viral load, is crucial to pandemic control. We documented comparable performance (96%) of two rapid test to standard RT‐qPCR. Lower cost and immediate results of rapid antigen tests may allow innovative containment measures or, at least, complement current testing limitations, specially in resource limited setting.