Positive Prostate-Specific Antigen (PSA) Results in Semen-Free Samples

The use of membrane test kits for detecting prostate specific antigen (PSA) during the forensic identification of semen has become a routine procedure in forensic labs across North America. During the validation of the "Seratec® PSA Semiquant" membrane test kit (Gesellschaft für Biotechnologie, Germany) at The Centre of Forensic Sciences, the sensitivity of the kits was found to be approximately 100 times greater than crossed-over electrophoresis. It also approached the reported sensitivity for detecting PSA through the enzyme-linked immunosorbent (ELISA) assay. As with any validation study of a new test procedure, it is a requirement that the specificity of that procedure be determined. It was during this aspect of our validation study that we obtained a positive PSA result from semen-free vaginal samples and also with a commercially available contraceptive foam. The validation results and interpretation guidelines for when the kits are used at the Centre of Forensic Sciences are outlined.