Table 2.

Relationship between likelihood of testing positive, test performance, PPV, and NPV for symptomatic people

	Predictive values		Distribution of test outcomes among 10 000 people tested
	PPV	NPV	True positive	False positive	True negative	False negative
25% likelihood of testing positive
80% sensitivity, 97% specificity	90%	94%	2000	225	7275	500
80% sensitivity, 98% specificity	93%	94%	2000	150	7350	500
80% sensitivity, 99% specificity	96%	94%	2000	75	7425	500
90% sensitivity, 99% specificity	97%	97%	2250	75	7425	250
50% likelihood of testing positive
80% sensitivity, 97% specificity	96%	83%	4000	150	4850	1000*
80% sensitivity, 98% specificity	98%	83%	4000	100	4900	1000*
80% sensitivity, 99% specificity	99%	83%	4000	50	4950	1000*
90% sensitivity, 99% specificity	99%	91%	4500	50	4950	500

People presenting for care or at testing centres. NPV=negative predictive value. PPV=positive predictive value.

^*Mitigation strategy is to confirm negatives.