Table 2.

Predictive Value of Serologic Testsa

Test ResultDisease PresentDisease AbsentTotal
Patients with 1% pretest probability of disease
 Positive959901,085
 Negative58,9108,915
 Total1009,90010,000
 Predictive value8.8b99.9c
Patients with 10% pretest probability of disease
 Positive9509001,850
 Negative508,1008,150
 Total1,0009,00010,000
 Predictive value51.4b99.4c
Patients with 50% pretest probability of disease
 Positive4,7505005,250
 Negative2504,5004,750
 Total5,0005,00010,000
 Predictive value90.5b94.7c
  • a Results are for the theoretical population of 10,000 persons and are given as numbers, except for predictive values, which are percentages. In each case, the test is 95% sensitive and 90% specific.

  • b Predictive value of a positive test result.

  • c Predictive value of a negative test result.