Table 1.

Performance of antigen test

	All data			Ct S gene <33			Ct ORF1 gene <33
Prevalence	Sample prev = 0.04	Prev = 0.005	Prev = 0.001	Sample prev = 0.04	Prev = 0.005	Prev = 0.001	Sample prev = 0.04	Prev = 0.005	Prev = 0.001
Sensitivity	68.9 (55.7–80.1)			77.8 (64.4–88.0)			79.2 (65.9–89.2)
Specificity	99.9 (99.9–100.0)			99.9 (99.6–100.0)			99.9 (99.6–100.0)
PPV	97.7 (98.0–99.0)	82.1 (39.1–97.0)	47.8 (11.3–86.7)	97.7 (85.5–99.7)	83.8 (42.1–97.4)	50.8 (12.6–88.0)	97.7 (85.4–99.7)	84.1 (42.6–97.4)	51.3 (12.9–88.2)
NPV	98.6 (85.5–99.7)	99.8 (99.8–99.9)	100.0 (100–100)	99.1 (98.5–99.5)	99.9 (99.8–99.9)	100.0 (100–100)	99.2 (98.6–99.5)	99.9 (99.8–100)	100.0 (100–100)

Overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the antigen test. In brackets, the exact binomial 95% confidence interval is reported. The PPV and NPV are presented assuming a prevalence of 0.04, as observed in the hospital surveillance study, as well as at the lower prevalence values of 0.005 and 0.001