Chlamydia trachomatis and Pap testing from a single, fluid-based sample: A multicenter study

OBJECTIVE: To determine the potential for both Pap testing and the Chlamydia direct fluorescence assay (DFA) from a single sample using the fluid-based ThinPrep® Pap Test™ method (Cytyc Corporation, Boxborough, Massachusetts). STUDY DESIGN: Conventional DFA was compared to ThinPrep® DFA in a direct-to-vial, double-blinded, multicenter protocol. Cervical scrapings were collected for the ThinPrep® Pap Test, and then a second swab was used to collect an endocervical sample for a conventional DFA test. The DFA slide prepared from the ThinPrep® Test and the conventional DFA sample prepared from the endocervical swab were evaluated independently. Discrepant cases were adjudicated by testing residual specimens using a Chlamydia direct DNA method. RESULTS: Combining 636 adequate cases (94% of the total collected), 582 (91.5%) were negative on both slides, 43 (6.8%) positive by both and 11 (1.7%) discrepant. The prevalence of Chlamydia was 7.9% based on the conventional DFA method (range, 4.3-10.9%). McNemar's two-tailed test indicated the results not to be statistically different (P>.05). Adjudication favored ThinPrep® 45% of the time and conventional 55%. Specimen adequacy favored ThinPrep with high statistical significance (McNemar's test, P>.01). CONCLUSION: A second slide prepared from the same vial of cells as that used for the ThinPrep® Pap Test can be used for Chlamydia testing by DFA. Fluid-based collection could allow multiple tests from a single sample.