COVID infection after a positive rapid antigen test

Probability:
32.9%
Odds:
1 to 2
dBan
−3.1 dBan

In this hypothetical group of 100,000 people at 0.5% prevalence, about 890 test positive: 293 are infected and 597 are false positives. For this scenario, a positive result corresponds to about a one-in-three chance of infection.

Calculation

p = (0.005 × 0.586) / [(0.005 × 0.586) + (0.995 × (1 − 0.994))] ≈ 0.3292

Assumptions

The calculation starts from the hypothetical 0.5% prevalence and uses pooled sensitivity 0.586 and specificity 0.994 for asymptomatic people with suspected exposure. These historical pooled estimates combine different tests and studies through February 2022. Performance varies by kit, timing, sampling, and setting. This calculation is not a personal diagnosis.

Sources

  1. Cochrane: accuracy of rapid antigen tests for COVID-19 Dinnes et al., version 4, published 28 November 2025, with studies searched through 17 February 2022