PSA Test : Dosage, Rate and Interpretation

Summary :

◉ Physiology

The prostate is a small gland that is part of the male reproductive system. It is located under the bladder and produces fluid that is part of semen.

PSA is a molecule secreted exclusively by the prostate. It exists in the semen where it has a role in the liquefaction of the seminal coagulum. Part of the secreted PSA passes into the bloodstream at concentrations one million times lower than its prostatic concentration.

A part of the blood PSA is free (approximately 70%), the other associated with blood proteins (approximately 30%). We then speak of “free PSA” or “complexed PSA”.

Prostate tumors are pathological overgrowths of part of this organ, producing higher amounts of detectable PSA in the blood.

Note: A gradual increase in PSA levels is observed with age.

◉ Requirements for a PSA test

The assay is done on a blood test, it is not necessary to be fasting (unless your blood sample will be used for additional tests).

You will need to avoid having sex or masturbating for 24 hours before your test, as the release of semen can raise your PSA level.

5-alpha-reductase inhibitors used for the treatment of voiding dysfunction associated with benign prostatic hyperplasia reduce the PSA value by half after 6 months of treatment.

There are several prostate specific antigen assay methods for which the result varies significantly. This is why it is essential to carry out the follow-up in the same laboratory or, failing that, with the same technique.

The tests allow either the determination of total PSA, or only its free fractions (Free PSA) or bound (complexed PSA).

◉ PSA blood test levels

Laboratories measure the amount of PSA in your blood. The results of the analysis are expressed in nanograms per milliliter of blood (ng/mL) or micrograms per liter (μg/L).

High PSA levels could be a sign of prostate cancer or another condition such as prostatitis or an enlarged prostate.

Although "normal" PSA levels vary from lab to lab (the lab report should always specify the assay method used), it is generally accepted that a lower value at 4 ng/ml is normal.

Note: The normal PSA level varies depending on the age of the patient, but according to AFU, tables of PSA values adjusted for age have little interest in individual practice, except in age groups under 60 years.

◉ Results interpretation

◾ In first intention, practitioners prescribe a dosage of total PSA (free PSA + complexed PSA).

The PSA test can detect elevated levels of PSA in the blood, but does not provide accurate diagnostic information about the condition of the prostate.

This protein is specific to the prostate but not to prostate cancer since other pathologies such as benign prostatic hyperplasia, inflammation or infection will modify the serum level.

What causes a high PSA value?

◾ If your PSA results are borderline (4 to 10), measuring the ratio of free PSA to total PSA is useful for assessing the risk of prostate cancer.


◉ High PSA levels, what to do?

High PSA levels can mean cancer or a non-cancerous condition such as a prostate infection, which can be treated with antibiotics.

If your PSA levels are higher than normal, your doctor will likely order more tests, including:


  1. R. Boissier - L'antigène spécifique de la prostate ou PSA
  2. Ross Krasnow - Should Men Get a PSA Test to Screen for Prostate Cancer and When
  3. PCF - The Prostate-Specific Antigen (PSA) Test
  4. Testing - Prostate Specific Antigen (PSA)
  5. HAS - Détection précoce du cancer de la prostate Actualisation du référentiel de pratiques de l'examen périodique de santé (EPS)
  6. C COULANGE - Du bon usage du PSA (Antigène Prostatique Spécifique) : recommandations de l'Association Française d'Urologie
  7. A. Villers - Dépistage du cancer de la prostate