(PSA) Prostatic Specific Antigen Ratio Test

Description of the Test

• The PSA Ratio Test measures the ratio between free PSA and total PSA in the blood.

• PSA is a protein produced by the prostate gland, and its levels can rise in cases of prostate cancer, benign prostatic hyperplasia (BPH), or inflammation.

• The ratio of free PSA to total PSA helps differentiate between benign prostate conditions and potential malignancy.

Purpose / Clinical Significance

• Used as a refinement tool in prostate cancer screening, particularly when total PSA levels fall in a borderline range.

• Helps reduce unnecessary biopsies by improving specificity compared to total PSA alone.

• Provides a better understanding of prostate health, especially in older men or those at risk of prostate disease.

• Supports urologists in assessing whether elevated PSA levels are due to cancer or non-cancerous causes.

Principle

• PSA exists in the blood in two major forms: free (unbound) and complexed (bound).

• The PSA Ratio Test calculates the percentage of free PSA relative to total PSA.

• A lower free-to-total PSA ratio may suggest a higher risk of prostate cancer, while a higher ratio is more consistent with benign conditions.

Whom and Why Should Take This Test

• Men with elevated total PSA levels, particularly between 4–10 ng/mL, where diagnosis is unclear.

• Individuals with a family history of prostate cancer or those at increased genetic risk.

• Men over the age of 50 as part of routine prostate screening, especially if total PSA is elevated.

• Patients with urinary symptoms, including frequent urination, weak stream, or nocturia, to evaluate prostate status.

• Those advised by their doctor to assess the need for prostate biopsy based on borderline PSA results.

Specimen Requirements

• A venous blood sample is collected, typically from the arm.

• No special preparation is required, though some labs may recommend avoiding ejaculation or vigorous exercise 24–48 hours prior to testing.

• Blood should be processed promptly to ensure accurate separation and measurement of free and total PSA.

• Ideally, the test should be avoided soon after prostate manipulation or infection, which may temporarily elevate PSA.

Common Methods

• Immunoassays, such as chemiluminescent immunoassay (CLIA) or electrochemiluminescence (ECL), are commonly used.

• Both free and total PSA are measured from the same blood sample, and the ratio is calculated as a percentage.

• Automated systems provide high accuracy and consistency for PSA ratio analysis.

Interpretation of Results

• A low free PSA ratio (often below 10–15%) suggests an increased risk of prostate cancer and may indicate the need for further evaluation.

• A higher free PSA ratio (typically above 25%) indicates a greater likelihood of a benign condition like BPH.

• The ratio provides context to total PSA levels, especially when total PSA falls within a grey zone.

• Results must be interpreted in combination with digital rectal exams (DRE) and clinical history.

Reference Range

• Normal PSA Ratio ranges may vary slightly between laboratories.

• A free-to-total PSA ratio of greater than 25% is usually considered low risk, while below 10% is considered high risk for prostate cancer.

• The reference range is only meaningful when total PSA falls in a moderate range (often 4–10 ng/mL).

• Age-specific reference ranges may apply, and trends over time are also significant.

Limitations

• PSA levels can be temporarily elevated due to infection, ejaculation, recent prostate procedures, or vigorous physical activity.

• The ratio alone cannot confirm or rule out cancer, but helps guide the decision to biopsy.

• Certain medications, such as 5-alpha-reductase inhibitors, may affect PSA readings.

• The test is less useful when total PSA is very high or very low.

Follow-up Testing

• If PSA ratio suggests elevated cancer risk, a prostate biopsy may be recommended.

• Multiparametric MRI of the prostate may be used before biopsy to better localize suspicious areas.

• Repeat PSA and PSA ratio testing may be done periodically to monitor trends over time.

• Digital rectal exams (DRE) and other prostate health assessments may be included in ongoing evaluation.

Conclusion
The PSA Ratio Test offers an advanced and informative approach to evaluating prostate health, particularly for men in Dubai undergoing routine screening or monitoring for prostate disease. By comparing free PSA to total PSA, it improves the accuracy of prostate cancer risk assessment and reduces unnecessary procedures. This test is especially helpful when PSA levels are ambiguous and further clarity is needed to make informed decisions about prostate biopsies.