Evaluation of prostate-specific antigen (PSA) membrane test assays for theforensic identification of seminal fluid

Prostate specific antigen (PSA, also known as p30), a glycoprotein produced by the prostatic gland and secreted into seminal plasma, is a marker used for demonstrating the presence of seminal fluid. Methods for the detection of PSA include Ouchterlony double diffusion, crossover electrophoresis, roc ket immuno-electrophoresis, radial immunodiffusion, and ELISA. The extremel y sensitive ELISA technique can detect PSA in concentrations as low as appr oximately 4 ng/mL. However, all these techniques are cumbersome and time co nsuming to perform in forensic laboratories, especially when only a few sam ples per week are processed. Various membrane tests are currently used in c linical settings to screen a patient's serum for the presence of PSA at lev els greater than 4 ng/mL. In this study we evaluated three immunochromatogr aphic PSA membrane tests by analyzing semen stains stored at room temperatu re for up to 30 years, post-coital vaginal swabs taken at different time af ter intercourse, semen-free vaginal swabs, and various female and male body fluids, including urine. The data demonstrate that PSA membrane test assay s offer the same sensitivity as ELISA-based tests and provide a rapid appro ach for the forensic identification of seminal fluid, Furthermore, when the supernatant from a DNA extraction is used for the assay, there is essentia lly no DNA consumption for determining the presence of PSA in a forensic sa mple.