Prostate Specific Antigen, Free, Serum

Prostate Specific Antigen (PSA), Free, Serum – P0018a

Test Overview

The Free PSA test measures the level of unbound (free) prostate-specific antigen circulating in the blood. PSA is a protein produced by the prostate gland, and it exists in two forms:

• Bound PSA (attached to proteins)
• Free PSA (not attached)

This test is often used alongside Total PSA to improve diagnostic accuracy for prostate conditions.

Why This Test is Done

• Helps differentiate between benign prostate conditions and prostate cancer
• Evaluates borderline or moderately elevated PSA levels
• Assists in reducing unnecessary biopsies
• Monitors prostate health in men, especially above 50 years

Clinical Significance

• Lower Free PSA % → Higher risk of prostate cancer
• Higher Free PSA % → More likely benign conditions such as:
  • Benign Prostatic Hyperplasia (BPH)
  • Prostatitis

Doctors often calculate:

Free PSA / Total PSA ratio (%)

Who Should Take This Test

• Men with elevated Total PSA levels (4–10 ng/mL)
• Individuals with family history of prostate cancer
• Men experiencing symptoms like:
  • Difficulty urinating
  • Frequent urination (especially at night)
  • Weak urine flow

Sample Type

• Blood (Serum)

Preparation

• Fasting: Not required
• Avoid:
  • Ejaculation (24–48 hours before test)
  • Vigorous exercise (especially cycling)
  • Recent prostate examination (consult doctor)

Normal Reference (General Guide)

• Free PSA is interpreted relative to Total PSA
• Typical ratio interpretation:
  • >25% → Low cancer risk
  • 10–25% → Moderate risk
  • <10% → Higher risk

(Ranges may vary slightly by laboratory)

Limitations

• Not a standalone diagnostic test
• Results must be interpreted with:
  • Total PSA levels
  • Clinical examination
  • Imaging or biopsy (if needed)

Key Benefits

• Improves diagnostic precision
• Helps avoid unnecessary invasive procedures
• Supports early detection of prostate cancer