Generality
PSA - acronym of Prostate Specific Antigen, Italianized in Prostate Specific Antigen - is a protein synthesized by prostate cells.
Small concentrations of prostate antigen are normally present in the serum of all men and can be assessed by a simple blood test.
What's this
PSA is a quantifiable protein in blood, produced exclusively by the prostate . For this reason, prostate specific antigen can be used as an indicator of prostate diseases .
From the physiological point of view, the function of PSA consists in keeping the seminal fluid fluid after ejaculation, so that the spermatozoa can move more easily in the female genital tract.
Why do you measure
PSA is quantifiable in the blood and is used as a marker for potential prostate problems, also and above all in the examinations of early diagnosis of the male population.
The dosage of PSA is indicated periodically to all men, starting from 50 years of age. This exam, in fact, can help - in association with the urological or andrological examination - to identify forms of prostate cancer in the early stages.
PSA is a specific marker of the organ, but not of the pathologies that affect it; in fact, high levels are recorded both in the presence of benign conditions (a prostatitis, a benign prostatic hyperplasia etc.), and of neoplastic processes of the prostate.
Prostate cancer
Together with rectal exploration and transrectal or suprapubic ultrasound, PSA helps to identify prostate cancer, both benign and malignant.
In case of positivity, a prostatic control biopsy is usually performed.
In addition to the diagnosis, the verification of the prostate specific antigen is also performed after the detection of the tumor, to check the progress of the treatments or highlight the possible resumption of the pathology.
It should be kept in mind that PSA also increases in benign conditions, such as benign prostatic hypertrophy and prostatitis (inflammation of the prostate). In addition, specific prostate antigen also increases due to recent sexual activity, palpation of the prostate gland by specialist examination, use of catheters and intake of certain drugs, such as allopurinol.
To improve the diagnostic specificity of PSA, in cases where the limit value is exceeded, the free specific prostate antigen (free-PSA) is also measured.
Normal values
Under normal conditions, blood levels of PSA are found below 4 nanograms per milliliter of blood (reference range: 0.0-4.0 ng / ml).
However, if the prostate cells are damaged, the concentrations in the bloodstream may increase.
High PSA - Causes
High levels of PSA occur during various prostatic diseases, such as:
- Prostate cancer;
- BPH;
- Various forms of prostatitis (inflammation of the prostate);
The PSA values also increase for the following reasons:
- Senescence;
- After prostate surgery;
- Insertion of a catheter and specific diagnostic tests (such as rectal exploration, cystoscopy, prostatic biopsy, rectoscopy and colonoscopy);
- Traumatism on the prostate (prolonged use of the bicycle, riding the bike, riding etc.).
Obesity has been related to a lowering of circulating PSA.
Low PSA - Causes
A 50% reduction in PSA levels is found in men taking 5-alpha reductase inhibitors (such as finasteride and dutasteride), a class of drugs used in the treatment of benign prostatic hypertrophy and baldness.
How to measure it
Concentrations of prostate specific antigen are measured in the laboratory after a simple blood sample.
Preparation
The patient can undergo blood sampling after a 3-hour fast.
To reduce the risk of error, it is important not to take the exam when you have a current urinary tract infection.
Furthermore, intense physical activity or sexual intercourse should not take place in the 48 hours prior to the PSA dosing, as both of these conditions can raise the blood levels of the parameter.
Interpretation of Results
Values of PSA and prostate cancer
The dosage of PSA in the plasma has a low degree of specificity : when its levels exceed a certain threshold (> 3-4 ng per ml of blood) very probably something does not work at the level of the prostate; however, in the absence of further diagnostic investigations, it is impossible to establish with certainty the benignity or malignancy of the condition.
| tPSA (ng / ml) | Probability of finding a prostate tumor |
| 0-4 | 10% (in 90% of cases it is a confined body form) |
| 4-10 | 25% (in 70% of cases it is a confined body form) |
| > 10 | 50% (in 50% of cases it is a confined body form) |
With reference to prostate cancer, the PSA dosage often returns false positives . These are cases in which high PSA values suggest the existence of prostate cancer, subsequently denied by various investigations. In other words, the finding of high levels of PSA is not sufficient to diagnose prostate cancer, especially in older men.
If the suspicion of cancer is confirmed by other diagnostic tests, the PSA dosage is a good indicator of tumor extension. In particular, when the PSA is only slightly increased or even normal it is unlikely that the tumor is very large.
Most men with high blood levels of prostate-specific antigen are not affected by cancer. Data in hand, only 25 - 35% of patients undergoing prostate biopsy (after finding high PSA) are actually carriers of prostate cancer, while a quarter of those affected by this form of cancer do not show significant increases in PSA.
Monitoring of specific prostate antigen is useful for assessing the patient's response to the therapy undertaken, which when accompanied is accompanied by a reduction in PSA values. The serum dosage must be performed before the other diagnostic tests, as these, as we have seen, can significantly increase the PSA values (after prostatic biopsy, increments can be registered up to 50 times, with a slow return to normality in the 30- 60 days thereafter).
Periodic monitoring of the PSA is very important. Repeated measurements can help to differentiate benign from malignant forms, the more likely the faster the increase in values. For this reason the concepts of PSA velocity and PSA doubling time have been introduced, both of which are not detectable by various elements, such as intra and interlaboratory variations, and biological ones not connected to the underlying pathology (a recent ejaculation, for example, can increase the blood levels of PSA).
Since their independence from prostate cancer is more likely in the presence of a marked hypertrophy of the gland, elevated PSA values can be related to prostate volume ( PSA density ).
Free PSA and PSA bound
Useful elements to evaluate the clinical significance of a high PSA can be collected by evaluating the proportion between free PSA and PSA linked to transport proteins . Indeed, it has been seen that benign conditions, such as prostatic hypertrophy, predominantly increase the free altitude, while prostate cancer mainly produces an increase in PSA bound.
Therefore, in a man who contrasts high levels of PSA tied to low values of free PSA, the presence of a prostate tumor is likely, while the opposite condition suggests a benign origin. In other words if:
- Relationship between free PSA / total low PSA (<0.20) → high risk of malignancy
- Relationship between free PSA / total normal or high PSA (> 0.20) → low risk of malignancy
In light of the above, the interpretation of PSA blood values is a very complex and constantly evolving subject, naturally reserved for expert urologists. Faced with a rise in PSA values, the doctor will therefore have to examine a whole series of elements, in order to direct the patient towards specific diagnostic tests, personalized treatments and simple periodic monitoring.
PSA Video - PSA and PSA High Values - Causes
X Problems with video playback? Reload from YouTube Go to Video Page Go to Wellness Destination Watch the video on youtube** Thompson IM, Pauler DK, Goodman PJ, Tangen CM, Lucia MS, Parnes HL, Minasian LM, Ford LG, Lippman SM, Crawford ED, Crowley JJ, Coltman CA (May 2004). "Prevalence of prostate cancer among men with a prostate-specific antigen level <or = 4.0 ng per milliliter". N. Engl. J. Med. 350 (22): 2239-46.
