Chlamydial infection in a high-risk population: Comparison of amplicor PCR and Gen-Probe PACE II for diagnosis

The objective of this study was to compare the sensitivities and specificities of two molecular techniques, polymerase chain reaction (Amplicor) and DNA hybridization probe (Gen-Probe PACE II), for the detection of Chlamydia trachomatis in cervical specimens. A total of 378 cervical specimens were collected from 189 female adolescent patients and tested with either Amplicor or Gen-Probe PACE II. Sociodemographic data and sexually transmitted disease risk behavior were also collected from patient charts and analyzed. The population comprised young adolescents (mean age 17.7) who were sexually active (77.1% had one or more partners in the last 3 months) with a relatively long duration of sexual activity (mean 2.8 years). The prevalence rates of cervical C. trachomatis infection diagnosed by Amplicor and Gen-Probe PACE II were 7.9 and 9.0%, respectively. Patients testing positive for C. trachomatis had a significant percentage of Pap smears with inflammatory results (p < 0.005). After initial testing, Amplicor had a sensitivity of 82.4% and a specificity of 93.3%, whereas Gen-Probe PACE II had a sensitivity of 99.4% and a specificity of 98.3%. After discrepant analysis, Amplicor and Gen-Probe PACE II had an equal sensitivity of 93.7%; the specificities were 100 and 98.8%, respectively. However, Gen-Probe PACE II had a 1% false-positive rate. Both Amplicor and Gen-Probe PACE II are highly sensitive. However, Amplicor is more specific and can be used as a confirmatory test. Either test for C. trachomatis may be indicated in patients with abnormal Pap smears.