A comparative analysis of accuracy and sensitivity in semen presumptive testing: ABAcard P30™, RSID Semen™, and Seratec PSA™

Abstract

Semen presumptive tests are often used in forensics to detect the possible presence of semen on evidence from a crime scene. These tests work by identifying enzymes or proteins commonly found in semen, such as prostate-specific antigen (PSA) and semenogelin. However, presumptive tests can produce false positive results, as these biomarkers may also be present in other bodily fluids. Despite this limitation, some agencies still rely on presumptive test outcomes as a confirmation test for semen in legal proceedings. This study evaluated and compared the accuracy and sensitivity of three rapid immunochromatographic test kits for semen detection: Rapid Stain Identification Series (RSID) Semen™, Seratec PSA™, and ABAcard P30™. The RSID Semen™ test detects semenogelin, while Seratec PSA™ and ABAcard P30™ detect PSA. Samples tested included serial dilutions of semen, as well as an array of bodily fluids and materials that could potentially cause false positive results. All samples were tested in triplicate with each kit. The study found differences in sensitivity between the three test kits, with false positives occurring to some degree with all methods. RSID Semen™, Seratec PSA™, and ABAcard P30™ all had issues detecting semen in a 1:10,000 dilution. Additionally, RSID Semen™ could not detect semen when it was mixed with dirt. There was an issue of non-specificity with all three of the test kits with various absorbent hygiene products. RSID Semen™, Seratec PSA™, and ABAcard P30™ all had several false positive test results with tampons, menstrual pads with blood, and diapers with urine samples. Additionally, ABAcard P30™ had false positive test results with female urine samples. These findings highlight the need for caution when using presumptive semen test results, especially as primary evidence in legal cases. These test kits should no longer be used as a confirmatory test for semen in legal proceedings. The data generated will help forensics investigators determine which test kit may be most appropriate and reliable for detecting semen on different types of evidence, highlighting the potential for false results. Using precise testing methods is critical for drawing correct conclusions during criminal investigations. While Seratec PSA™ showed the highest sensitivity among the test kits evaluated, it had a concerning false positive rate of 12%, the highest rate observed. Of the three rapid semen detection kits compared, the ABAcard P30™ kit displayed the highest degree of accuracy. ABAcard P30™ had both the lowest false positive rate at 6% and the second-lowest false negative rate at 2% out of the kits tested, indicating superior sensitivity and specificity.