PSA
Overview
Prostate-specific antigen (PSA) is a glycoprotein enzyme produced primarily by prostate epithelial cells, measuring serum levels that reflect prostate gland activity and integrity. It functions in liquefying semen and is released into the bloodstream in small amounts, with elevations often indicating prostate cell disruption or proliferation. High PSA levels may signal prostate cancer, benign prostatic hyperplasia (BPH), or prostatitis, while low levels are typical in healthy individuals or post-prostatectomy; it is clinically useful for prostate cancer screening, monitoring treatment response, and detecting recurrence in at-risk populations.
Clinical Use Cases
- Screening for prostate cancer in men over 50 or with risk factors.
- Monitoring disease progression or recurrence after prostatectomy or radiation.
- Evaluating treatment efficacy in prostate cancer therapy.
- Differentiating BPH, prostatitis, or other non-malignant conditions.
- Assessing risk in biopsy decision-making with tools like PSA density or velocity.
Specimen Types
- Serum (primary).
- Plasma.
- Whole blood.
Measurement Methods
- Immunoassays (e.g., chemiluminescent, enzyme-linked).
- Automated analyzers (e.g., Roche, Abbott platforms).
- Total PSA assays (standard).
- Free PSA assays (for ratio calculation).
Test Preparation and Influencing Factors
- Avoid ejaculation, vigorous exercise, or prostate manipulation (e.g., DRE, biopsy) for 48 hours prior.
- No fasting required.
- Influenced by age, race, medications (e.g., 5-alpha reductase inhibitors lower PSA).
- Urinary tract infections, recent catheterization, or trauma elevate levels.
- Diurnal variation minimal.
Synonyms
- Prostate-specific antigen.
- Gamma-seminoprotein.
- Kallikrein-3 (KLK3).