SARS-CoV-2 Antigen Rapid Tests Show High False-Positive Rates When Screening Asymptomatic Healthcare Workers
A multicentre post-implementation study evaluated 71,847 antigen-based point-of-care tests across 369 Canadian continuing care sites screening asymptomatic healthcare workers. The overall detection rate was only 0.05% true positive, with the BD Veritor yielding 76.6% false positives (PPV 23.4%) compared to 30.0% false positives for the Abbott Panbio (PPV 70.0%). The findings highlight the critical importance of prevalence-dependent positive predictive value when deploying rapid antigen tests in low-prevalence screening programmes.
The original study
Multicenter Postimplementation Assessment of the Positive Predictive Value of SARS-CoV-2 Antigen-Based Point-of-Care Tests Used for Screening of Asymptomatic Continuing Care Staff.
- Authors
- Kanji JN, Proctor DT, Stokes W, Berenger BM, Silvius J, Tipples G, et al.
- Journal
- Journal of clinical microbiology
- Type
- Journal Article, Multicenter Study
- PMID
- 34288728
Original abstract
Frequent screening of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among asymptomatic populations using antigen-based point-of-care tests (APOCTs) is occurring globally with limited clinical performance data. The positive predictive value (PPV) of two APOCTs used in the asymptomatic screening of SARS-CoV-2 among health care workers (HCWs) at continuing care (CC) sites across AB, Canada, was evaluated. Between 22 February and 2 May 2021, CC sites implemented SARS-CoV-2 voluntary screening of their asymptomatic HCWs. On-site testing with Abbott Panbio or BD Veritor occurred on a weekly or twice-weekly basis. Positive APOCTs were confirmed with a real-time reverse transcriptase PCR (rRT-PCR) reference method. A total of 71,847 APOCTs (17,689 Veritor and 54,158 Panbio) were performed among 369 CC sites. Eighty-seven (0.12%) APOCTs were positive, of which 39 (0.05%) were confirmed as true positives using rRT-PCR. Use of the Veritor and Panbio resulted in 76.6% and 30.0% false-positive detection, respectively (P < 0.001). This corresponded to PPVs of 23.4 and 70.0% for the Veritor and Panbio, respectively. Frequent screening of SARS-CoV-2 among asymptomatic HCWs in CC, using APOCTs, resulted in a very low detection rate and a high rate of detection of false positives. Careful assessment of the risks versus benefits of APOCT programs and the prevalence of infection in this population needs to be thoroughly considered before implementation.