Evaluation of prostate-specific antigen as a quantifiable indicator of condom failure in clinical trials

The ability of condoms to retain all elements of semen during intercourse has been assessed by postcoital visual inspection and in vitro permeability studies. Yet, these observations may not be sufficiently precise or realistic. This pilot study evaluated prostate-specific antigen (PSA) as a semen marker of inapparent failure of the condom barrier under conditions of actual use. Twelve couples collected samples from the vagina and surfaces of the condom using sterile cotton swabs. We obtained precoital and postcoital samples for 24 acts of unprotected intercourse, 54 acts of intercourse using intact condoms, and 40 acts of intercourse using condoms that had been deliberately punctured. We used electrophoresis to determine the amount of PSA present in the samples. PSA was detected in 100% (24/24) of vaginal samples collected immediately after unprotected intercourse and in none of the vaginal samples collected more than 24 h after intercourse (0/90). PSA was also present in 98% (83/85) of the samples collected from the inside of the condom that had failed during intercourse. Excluding uses where the condom failed during intercourse, PSA was detected in 2% (1/47) of the postcoital vaginal samples collected after use of intact condoms and in 41% (14/34) of the samples collected after use of condoms with known 1-mm punctures. We conclude that PSA shows great promise as a semen biomarker in clinical trials of barrier methods. We recommend that future studies further investigate the ability of this biomarker to identify condom failures and quantify the extent of semen exposure associated with various types of condom failures.