Extended development of RSID-Semen and SERATEC PSA Semiquant assays with diluted semen samples
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Citation
Abstract
In sexual assault cases, forensic scientists routinely employ assays to detect cellular material and proteins, such as spermatozoa and acid phosphatase (AP), to identify biological material, notably semen, on items of evidence. Due to the limit of detection (LOD) for all chemical presumptive tests and confirmatory immunochromatographic assays, more diluted samples may not be detected when testing for the presence of proteins such as prostate-specific antigen (PSA) and semenogelin (Sg). The concentrations of the various elements in semen can differ significantly from person to person due to many factors including lifestyle and genetic conditions. The variable concentrations of different seminal components between individuals result in a wide range of protein and cellular material detection in semen stains. Negative immunochromatographic assay results, in conjunction with azoospermia, or the absence of spermatozoa, during microscopic evaluations, can falsely lead forensic serologists to conclude the absence of semen on evidentiary items. By testing different sample dilutions bordering the LOD of both RSID™-Semen (Independent Forensics, Hillside, IL) and SERATEC® PSA Semiquant (SERATEC GmbH, Göttingen, Germany), this study demonstrates the potential to increase the detection rate of Sg when extending the development period beyond the suggested 10 minutes. Although PSA detection did not improve with extended testing time, Sg detection increased, resulting in positive results developing between 10 and 45 minutes. The 45-minute time limit of this study takes into consideration the large backlog of cases at laboratories and attempts to mediate the balance between increased time expenditure and improved detection rates.
Description
2024