Positive prostate-specific antigen (PSA) reaction in post-mortem rectal swabs: A cautionary note☆

Abstract 

Prostate-specific antigen (PSA) tests are considered a valuable screening method for the forensic examination of semen in vaginal and rectal swabs of alleged victims of sexual abuse. Although these membrane tests have been also applied to autopsy specimens no study has assessed their reliability when performed on post-mortem (PM) rectal swabs from decomposed cadavers. The present study describes the results obtained with the Seratec^® PSA Semiquant Kit test on 39 male and 10 female adult cadavers with no history of sexual assault and with a PM interval up to 136days. Overall 64% of the 39 male cadavers tested positive for the PSA, the positive PSA reaction being more frequent in the 20 males with advanced decomposition than in the 19 males with no putrefaction signs (70% vs. 58%). The Phosphatesmo KM Paper Test^® for detection of acid phosphatase (AP) gave a positive color reaction with 60% of the rectal swabs obtained from decomposed male cadavers. Both the PSA-test and the Phosphatesmo KM paper-test gave a negative result in each of the rectal samples from female cadavers. Y STR multiplex revealed no DNA other than that of the subject tested in the rectal swab positive for PSA. The results of the present study show that PSA membrane tests are unreliable and can be misleading when derived from male rectal samples obtained at autopsy.

Keywords: Forensic biology, Prostate-specific antigen, Rectal swabs, Autopsy