• Susannah L McKay, Farrell A Tobolowsky, Erin D Moritz, Kelly M Hatfield, Amelia Bhatnagar, Stephen P LaVoie, David A Jackson, K Danielle Lecy, Jonathan Bryant-Genevier, Davina Campbell, Brandi Freeman, Sarah E Gilbert, Jennifer M Folster, Magdalena Medrzycki, Patricia L Shewmaker, Bettina Bankamp, Kay W Radford, Raydel Anderson, Michael D Bowen, Jeanne Negley, Sujan C Reddy, John A Jernigan, Allison C Brown, L Clifford McDonald, Preeta K Kutty, and CDC Infection Prevention and Control Team and the CDC COVID-19 Surge Laboratory Group.
• Centers for Disease Control and Prevention, Atlanta, Georgia (S.L.M., F.A.T., E.D.M., K.M.H., A.B., S.P.L., D.A.J., J.B., D.C., B.F., S.E.G., J.M.F., M.M., P.L.S., B.B., K.W.R., R.A., M.D.B., S.C.R., J.A.J., A.C.B., L.C.M., P.K.K.).
• Ann. Intern. Med. 2021 Jul 1; 174 (7): 945-951.

BackgroundTo address high COVID-19 burden in U.S. nursing homes, rapid SARS-CoV-2 antigen tests have been widely distributed in those facilities. However, performance data are lacking, especially in asymptomatic people.ObjectiveTo evaluate the performance of SARS-CoV-2 antigen testing when used for facility-wide testing during a nursing home outbreak.DesignA prospective evaluation involving 3 facility-wide rounds of testing where paired respiratory specimens were collected to evaluate the performance of the BinaxNOW antigen test compared with virus culture and real-time reverse transcription polymerase chain reaction (RT-PCR). Early and late infection were defined using changes in RT-PCR cycle threshold values and prior test results.SettingA nursing home with an ongoing SARS-CoV-2 outbreak.Participants532 paired specimens collected from 234 available residents and staff.MeasurementsPercentage of positive agreement (PPA) and percentage of negative agreement (PNA) for BinaxNOW compared with RT-PCR and virus culture.ResultsBinaxNOW PPA with virus culture, used for detection of replication-competent virus, was 95%. However, the overall PPA of antigen testing with RT-PCR was 69%, and PNA was 98%. When only the first positive test result was analyzed for each participant, PPA of antigen testing with RT-PCR was 82% among 45 symptomatic people and 52% among 343 asymptomatic people. Compared with RT-PCR and virus culture, the BinaxNOW test performed well in early infection (86% and 95%, respectively) and poorly in late infection (51% and no recovered virus, respectively).LimitationAccurate symptom ascertainment was challenging in nursing home residents; test performance may not be representative of testing done by nonlaboratory staff.ConclusionDespite lower positive agreement compared with RT-PCR, antigen test positivity had higher agreement with shedding of replication-competent virus. These results suggest that antigen testing could be a useful tool to rapidly identify contagious people at risk for transmitting SARS-CoV-2 during nascent outbreaks and help reduce COVID-19 burden in nursing homes.Primary Funding SourceNone.

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