Table 2:
Predicitive Value, High Prevalence
Syndrome Present
Syndrome Not Present
Positive test
95
10
Negative test
5
90
100
100
200
Sensitivity 0.95, specificity 0.90, prevalence 0.50. Positive predictive value 95/ 95 + 10 = 0.90, i.e. the probability that the patient has the syndrome if this sign is present, is ninety per cent.