Prostate-Specific Antigen (PSA)
Definition
A serine protease glycoprotein (also called p30) secreted in high concentrations by the prostate gland into seminal plasma. The primary immunological marker for semen in forensic casework. Detected by antibody-based assays including ELISA and lateral-flow immunochromatographic strips.
- Also known as
- p30
- Chemical class
- Serine protease glycoprotein
- Source
- Prostate gland, secreted into seminal plasma
- Detection methods
- ELISA, lateral-flow immunochromatographic strips
- Evidence role
- Primary immunological marker for semen
Common questions
Is PSA testing in forensic casework the same test used in medical prostate cancer screening?+
The underlying antigen is the same protein, but forensic serology uses qualitative or semi-quantitative strip and ELISA formats built to confirm presence in a stain, while clinical PSA testing measures precise blood concentration for cancer monitoring, so the assay format and interpretation differ.
Why is PSA testing used alongside sperm cell microscopy rather than replacing it?+
PSA confirms the presence of seminal fluid even without intact sperm, which is essential in cases involving a vasectomized donor or a degraded sample, but combining it with sperm observation when sperm are present gives two independent lines of evidence that strengthen the overall conclusion.
Can PSA levels distinguish between different individuals the way DNA can?+
No. PSA testing only confirms that semen is present in a stain; it carries no individualising information about who deposited it, which is why a positive PSA result is always followed by separate DNA profiling to identify a specific source.
Related terms
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