Total + Free PSA

This panel is a set of blood tests that evaluates levels of prostate-specific antigen (PSA)—a protein made primarily by cells in the prostate gland. The test includes:

• Total PSA: Measures all circulating PSA, whether it is bound to other proteins or freely floating.
• Free PSA: Measures the portion of PSA that circulates freely in the blood.
• PSA Ratio (also called % Free PSA): Calculated as Free PSA divided by Total PSA, expressed as a percentage. This ratio can help differentiate between benign prostate conditions and prostate cancer.

The Biology Behind PSA

PSA is a serine protease enzyme secreted by prostate cells to liquefy semen, which helps sperm motility. Normally, only small amounts of PSA enter the bloodstream. However, when the prostate is enlarged, inflamed, or cancerous, PSA levels can rise. This makes PSA a valuable—but not perfect—biomarker for prostate health.

Benign conditions, such as benign prostatic hyperplasia (BPH) or prostatitis (inflammation of the prostate), can also increase PSA.

Prostate cancer typically causes higher total PSA levels and a lower percentage of free PSA compared to benign conditions.

This is where the PSA Ratio becomes especially helpful. A low PSA Ratio (e.g., <10–15%) may suggest a higher risk of prostate cancer, while a higher ratio is more consistent with benign conditions. However, interpretation must always consider age, prostate size, recent physical activity, infections, and even ejaculation—each of which can influence PSA levels.

When Is It Useful?

• Screening for prostate cancer, particularly in men over 50 or those with a family history of the disease.
• Monitoring prostate health in individuals with known prostate conditions.
• Guiding biopsy decisions: For men with elevated total PSA (e.g., 4–10 ng/mL), the PSA ratio helps assess whether further testing or a biopsy is warranted.

Important Caveats

• Not specific for cancer: PSA can rise for non-cancerous reasons, which is why it’s considered a risk indicator rather than a definitive diagnostic tool.
• Medications and procedures: Drugs like finasteride (for BPH or hair loss) can lower PSA levels, and recent procedures like cystoscopy or prostate massage can transiently increase PSA.
• Age-adjusted ranges: PSA levels tend to increase with age, so what’s considered “normal” varies.

Combining total, free, and ratio values improves the accuracy of PSA testing, offering a more nuanced picture than total PSA alone.