Upgraded diagnostic value of Gen-Probe PACE 2 assay for detection of Chlamydia trachomatis infection

In this study, we evaluate the performance of a nucleic acid amplification assay, COBAS AMPLICOR (Roche Molecular systems) (PCR), compared to non-amplified DNA probe assay PACE2 (Gen-Probe Inc.) for the detection of C. trachomatis in a total of 2,916 samples (2,114 females and 802 males) consecutively collected in two different clinical pathology laboratories, over a period of three years. In the females, the endocervical swabs showed a similar range of detection when using the two different methods: out of 1,581 females processed with PACE 2, 1.4% (2005), 0.9% (2006), 0.5% (2007), resulted positive for C. trachomatis; out of 533 females processed with PCR, 1.3% (2005), 1.5% (2006) and 1.2% (2007), resulted positive. However, in the male subjects we found an increased positivity of Chlamydia detection on urethral swabs by using PACE 2: 4.8% (2005), 1.9% (2006) and 2.9% (2007), compared to urine specimen processed by PCR: 1% (2005), 1.4% (2006) and 0% (2007). Even if PCR should be considered a most promising tool for routine diagnosis of Chlamydia infection, Gen Probe allowed us to better identify Chlamydia trachomatis (in 4.8% of urethral swabs compared to urine) leading to a hypothesis that extracellular EB forms of Chlamydia could be absent in urine in persistent infectious.