Prostate-specific antigen
PSA is a serine protease produced only in the prostate gland and, therefore, is an organ-specific marker. It is not cancer-specific however, as levels may also be elevated in benign conditions.
- Indications
- Suspected prostate cancer
- Monitoring for recurrence following treatment of prostate cancer
- Interpretation
- Total PSA levels (I.e. free and bound PSA)
- PSA > 4 ng/mL: Prostate cancer is likely.
- Free PSA (unbound) : Free PSA levels are lower in prostate cancer than in normal prostate tissue or benign disease.
- Total PSA levels (I.e. free and bound PSA)
- Other causes of elevated total PSA: BPH, UTI, prostatitis, prostatic trauma or manipulation (including DRE)
Warning
A PSA level ≤ 4 ng/mL does not exclude prostate cancer!
Warning
5-alpha reductase inhibitors (5-ARIs) can suppress PSA production, resulting in spuriously low PSA levels. This should be taken into consideration in patients on long-term 5-ARIs (e.g., for BPH).
Tip
Inflammation, manipulation of the prostate, and other malignant and benign prostate diseases may lead to a false-positive PSA result!