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 h as been assessed by postcoital visual inspection and in vitro permeability studies. Yet, these observations may not be sufficiently precise or realist ic. This pilot study evaluated prostate-specific antigen (PSA) as a semen m arker of inapparent failure of the condom barrier under conditions of actua l use. Twelve couples collected samples from the vagina and surfaces of the condom using sterile cotton swabs. We obtained precoital and postcoital sa mples for 24 acts of unprotected intercourse, 54 acts of intercourse using intact condoms, and 40 acts of intercourse using condoms that had been deli berately 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 vag inal samples collected more than 24 h after intercourse (0/90). PSA was als o present in 98% (83/85) of the samples collected from the inside of the co ndom that had failed during intercourse. Excluding uses where the condom fa iled during intercourse, PSA was detected in 2% (1/47) of the postcoital va ginal samples collected after use of intact condoms and in 41% (14/34) of t he samples collected after use of condoms with known I-mm punctures. We con clude that PSA shows great promise as a semen biomarker in clinical trials of barrier methods. We recommend that future studies further investigate th e ability of this biomarker to identify condom failures and quantify the ex tent of semen exposure associated with various types of condom failures. CO NTRACEPTION 1999;60:289-298 (C) 1999 Elsevier Science Inc. All rights reser ved.