Diagnosis - PSA and PAP Tests

These are blood tests that check the level of a protein, Prostate Specific Antigene (PSA) and an enzyme, Prostate Acid Phosphate (PAP).

The PSA test contributes to early diagnosis of the prostate tumor, and is made every year together with the Digital-Rectal Exploration of the Prostate.  It is specifically for the prostate, but not for the tumor, since it can increase in the course of benign prostate hypertrophy and in the course of prostatis.  It is the task of the Urologist to clarify when the PSA is suspicious for a tumor.

The Prostate Acid Phostate (PAP) is not used for early diagnosis of the prostate tumor but to control the response to therapy or the progression in  tumors that have spread.

The PSA test measures the quantity of protein in the blood in nanograms per milliliter (ng/mL).  A PSA level of 4 ng/mL or lower is considered normal; 4 to 10 ng/mL is moderately to highly suspicious (the PSA increases with age) ; 10 to 20 strongly suspicious; 20 to 35 very high, strongly suspicious.  Most men with moderately high levels of PSA do not have a prostate tumor but many men with prostate tumors have normal levels of PSA.

Very high levels can indicate the presence of a tumor.

The PSA test can give false results.  A False Positive is verified when the PSA level is high but the tumor is not present.  A False Negative is verified when the PSA level is normal and the tumor is present.  For this reason, if the PSA level is elevated or suspect, a biopsy is carried out to confirm or exclude the tumor diagnosis.

Free and total PSA
The PSA circulates in the blood both freely and linked to enzymatic inhibitors.  Total PSA is the sum of the levels of both forms; free PSA measures only the level of non-linked PSA.  Studies suggest that the malignant cells of the prostate produce total PSA; therefore, a low level of free PSA compared to total PSA could indicate a prostate with a tumor and a high level of free PSA compared to total PSA could indicate a healthy prostate, Benign Prostate Hypertrophy or simple Prostatitis.

Age and PSA
Data suggests that the level of PSA increases with age.  In men from 40 to 49 years of age, values of PSA up to 2.5 ng/mL are considered normal, and in the same way a value of 3.5 ng/mL for 50-59 years, a value of 4.5 ng/mL  in men between 60 and 69 and 6.5 for men 70 or over.  Not every doctors agree with these values.
The “Age/PSA” parameters and “PSA Velocity” (progressive increase in PSA from one year to another or in successive tests) are used to determine the risk of  a prostate tumor.