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.