Free PSA is a prostate tissue-specific protein used as a tumor marker for prostate cancer screening and diagnosis. It is found in:
- Normal prostate tissue
- Benign prostatic hyperplasia (BPH)
- Metastatic prostate cancer
- Prostatic fluid and ejaculate plasma
It is not detected in other cancers or tissues.
Key Characteristics of Free PSA
- Half-life: ~4 days
- Forms in the blood:
- Free PSA (not bound to α1-antichymotrypsin or other binding proteins, ~10% of total PSA)
- Bound PSA (complexed with antiproteases)
Biomaterial: Venous blood
Pre-test recommendations:
- Avoid fatty foods 24 hours before the test.
- Avoid physical and emotional stress for 30 minutes before the test.
- Do not smoke for 30 minutes before the test.
- Wait 6–7 days after:
- Prostate massage
- Digital rectal exam (DRE)
- Prostate biopsy
- Laser therapy
- Cystoscopy, colonoscopy
- Any mechanical intervention to the prostate
- Monitoring disease progression, early detection of metastases, and evaluating treatment effectiveness in prostate cancer
- Assessing the condition of patients with benign prostatic hyperplasia (BPH)
- Screening for prostate cancer in men over 50 years old
- Evaluation of patients with urinary symptoms (frequent, painful, or difficult urination)
- Assessing prostate enlargement and structural changes on imaging
Free PSA/Total PSA Ratio Interpretation
- <10% → High risk of prostate cancer
- >25% → Low risk of prostate cancer