PSA is an essential component of the seminal plasma and synthesized in the acinar cells of the ductal epithelium of the prostate gland, and then secreted in the ductal system where it reaches high concentrations.
Usually PSA is present in low concentrations in serum. In cases where microscopic alteration of the prostate occurs (cancer, benign prostatic hypertrophy, acute prostatitis, prostate biopsy) PSA will air in the stroma, from where it will reach the general circulation, lymphatic system and capillary path.
The prostate specific antigen is the most important marker in assessing prostate cancer and has utility in both detection and monitoring of the disease.
PSA is almost exclusively associated with prostate disorders, but it is not specific for prostate cancer, values have been found to be elevated in other conditions (enlarged prostate, prostatitis acute or chronic).
International recommendations on early detection of prostate cancer include PSA testing combined annual prostate exam (digital rectal examination) in men aged over 50 years with moderate risk. Screening at a younger age (40-45 years) is indicated only in those cases with a family history of prostate cancer (first degree relatives). Although PSA is the best laboratory test to detect prostate cancer, the result should always be interpreted together with clinical data provided by digital rectal examination. Interpretation of isolated PSA value can be confusing.
In patients with PSA between 4 and 10 ng / mL and negative digital rectal exam the marker should be evaluated in the same free-PSA serum. It turned out that the conduct of this test further reduces the number of unnecessary biopsies.
PSA has an important role in monitoring prostate cancer in its various stages: supervision, establishing therapeutic option, estimating prognosis and assessment of the effectiveness of treatment (surgery, hormonal). After radical prostatectomy PSA should drop to undetectable levels; persistently elevated PSA values indicate the presence of residual disease. Increased PSA levels after radical surgery is an indicator of relapse of the disease may precede clinical signs.
Free-PSA provides no relevant clinical information in monitoring prostate cancer, the test is not recommended to use for this purpose.
Method – ELISA
Normal values: 3.15 to 4.65 ng / ml
Total PSA – are dependent on age:
50-60 years: ≤ 3.1 ng / mL;
60-70 years: ≤ 4.1 ng / mL;
> 70 years: ≤ 4.4 ng / mL.
Free-PSA: percentage expressing the ratio of free PSA detected by the analyzer and total PSA.
If free-PSA is> 19% one can say with a sensitivity and a specificity of 82% that it is a benign prostatic hypertrophy.
The lack of specificity of this marker and the inability to determine the aggressiveness of the tumor are the most significant limitations of the PSA test in detecting prostate cancer. Approximately 25% of patients diagnosed with prostate cancer have values within normal, while 50% of men with benign prostatic hyperplasia show elevated levels of PSA.
Several large studies have concluded that the threshold of 4 ng / mL PSA is suitable for detection of prostate cancer. In Europe this threshold is commonly used both in clinical trials and in clinical practice.
Other benign prostate diseases which may be accompanied by increases in PSA are: acute or chronic prostatitis, prostatic infarction, retention of urine.
The effect on the level of PSA urological maneuvers:
• Rectal examination: may cause minor increases rarely clinically significant.
• Prostate Massage: may cause small increases in some patients.
• Transurethral Resection: cause significant increases (harvesting will be done after at least 6 weeks).
• Prostate Biopsy: cause significant increases (harvesting will be done after at least 6 weeks).
• Ultrasound: may cause increases in a small number of patients.
• Cystoscopy: apparently using flexible cystoscope does not change the PSA level, while using rigid cystoscope can cause elevated levels.
Ejaculation can cause transient increases in PSA.
After hormonal therapy PSA does not always reflect tumor behavior. Anti-androgen medication may cause low levels of PSA in the presence of residual disease.