Table 1

Worked example of a specific and sensitive test with low positive predictive value

Pop=100 000
Prevalence=1%
Sensitivity=99%
Specificity=99%
Infected (+)Not infected (−)PV
Positive test result (+)990990Positive PV=50%
Negative test result (−)1098 010Negative PV=99.99%
Total100099 000
  • PV, predictive value.