Improved performance of PACE 2 with modified collection system in combination with probe competition assay for detection of Chlamydia trachomatis in urethral specimens from males.

The Gen-Probe PACE 2 assay (GP) in combination with a modified collection system was compared with cell culture (CC) for the detection of Chlamydia trachomatis in urethral specimens from males. Analysis of discordant results was performed by PCR. The modifications, i.e., application of a more rigid swab type and a 50% reduction in the amount of transport medium, were made to improve the sensitivity of the assay. By using the modified GP on 302 urethral specimens from males, a sensitivity of 89.5% and a specificity of 100% were determined. In addition, performance of a probe competition assay on all GP samples with a result > 0.6 and < 1.0 times the cutoff factor (gray zone) detected three more true-positive samples. The sensitivity of GP in combination with the probe competition assay increased to 94.9%, with a specificity of 100%. This was identical to the performance of CC. The modified GP offers a very sensitive and specific alternative to CC.