Specificity and Predictive Value Positive. However, clinicians should be aware that even with these high specificities, false positive results account for an important pro-portion of all positive test results among groups of patients with a low prevalence of chlamydial infection. The PVP is the proportion of all persons who have a positive test result for a condition who actually have that condition. In chlamy-dia screening applications, the PVP is influenced primarily by the specificity of the test and the prevalence of chlamydia. Specificities of the nonculture tests have been Verifying Positive Screening Test Results.
Culture is the most sensitive and specific method for verifica-tion.
However, verification with culture requires a second specimen that is collected either at the time the first specimen is collected or during a return visit. Perform a second nonculture test that identifies a C. trachomatis antigen or a nucleic acid sequence that is different from that identified by the screening test. Theoretically, detecting a second, highly specific antigen or nucleic acid se-quence should provide adequate specificity for verification. However, this approach has had limited evaluation in field trials. A positive screening test may be verified by a second test using a second specimen that is collected either at the time the first specimen is collected or during a return visit.