Table 1.

Displayed are the predictive values of a positive test result, assuming maximal (100%) test sensitivity. (Real world sensitivity will be less, reducing the predictive value from that shown.) A range of test specificity values are in the first column. A range of pre-test probabilities, representing the estimated population prevalence, head the remaining columns.

	Prevalence in population to be tested (the pre-test probability)
Specificity	1 in 5 (20%)	1 in 10 (10%)	1 in 20 (5%)	1 in 100 (1%)	1 in 1000 (0.1%)	1 in 10,000 (0.01%)
90.0%	71.4%	62.6%	34.5%	9.2%	1.0%	0.1%
95.0%	83.3%	69.0%	51.3%	16.8%	2.0%	0.2%
98.0%	92.6%	84.7%	72.5%	33.6%	4.8%	0.5%
99.0%	96.2%	91.7%	84.0%	50.3%	9.1%	1.0%
99.9%	99.6%	99.1%	98.1%	91.0%	50.0%	9.1%