Forty women participated in three clinic visits during which they were exposed to their partner's semen (10 microL, 100 microL, and 1 mL). At each visit they took vaginal fluid samples before exposure to their partner's semen, immediately after, and at 1, 24, and 48 h after exposure. PSA was measured with an enzyme-linked immunoassay. The mean PSA level for preexposure swabs ranged between 0.43 and 0.88 ng/mL. The mean PSA levels were 193 immediately after exposure to 10 microL, 472 after 100 microL, and 19,098 after 1 mL. The PSA levels declined within 1 h, and returned to background at 48 h. The findings confirm that our procedure is a sensitive and specific method for detecting recent semen exposure, and indicate that PSA levels depend on exposure intensity and time since exposure. Application of this method in condom efficacy studies provides objective evidence of condom failure that enhances the interpretation of self-report.
PIP: This article examines the efficacy of prostate-specific antigen (PSA) in vaginal fluid as a biologic marker of condom failure. The sample included 40 women who participated in three clinic visits during which they were exposed to their partner's semen (10 mcl, 100 mcl, and 1 ml). At every clinic visit, vaginal fluid samples were taken before exposure with their partner's semen, immediately after, and at 1, 24, and 48 hours after exposure; PSA was measured with an enzyme-linked immunoassay. A 0.43-0.88 ng/ml mean PSA level was found in preexposure swabs, while the mean PSA levels were 193 ng/ml immediately after exposure to 10 mcl, 472 ng/ml after exposure to 100 mcl, and 19,098 ng/ml after exposure to 1 ml. The PSA levels declined within 1 hour and returned to an original state at 48 hours. Findings show that the procedure is a sensitive and specific method for detecting recent exposure to semen and indicate that the signal intensity is a function of semen exposure and time since exposure. Application of this procedure in studies of condom efficacy provides objective evidence of condom failure, which improves the interpretation of self-reports.