Radioimmunoassay of human prostate-specific acid phosphatase. A sensitive and specific assay for semen detection in forensic medicine.

Human prostate-specific acid phosphatase was measured by a rapid and sensitive radioimmunoassay in samples which originated from investigations of suspected sexual assaults and in which microscopic examination did not show sperm cells. Of the 12 samples, Ouchterlony double immunodiffusion showed the presence of spermatic fluid in three samples, whereas radioimmunoassay detected an additional seven spermatic fluid-positive ones. It is also shown that the procedure is sensitive enough for forensic medical purposes to detect semen in highly diluted postcoital vaginal fluid, and no cross-reactivity with nonseminal samples tested was observed.