PSA - Prostate specific antigen
What is PSA?
L'Specific Prostate Antigen - or PSA, Prostate Specific Antigen - is a glycoprotein produced exclusively by the cells of the prostate gland and secreted in the seminal fluid. Its function is to liquefy the seminal fluid more, to allow the spermatozoa a greater motility within it.
The test of Total PSA (PSA reflex) is carried out in the laboratory through a simple withdrawal of blood, usually after a first urological visit. The patient is advised to arrive in the morning on an empty stomach from the previous evening and not to engage in intense physical activity or any type of sexual intercourse in the 48 hours prior to blood collection, as these conditions are associated with an increase in the circulating levels of this glycoprotein. It is also not recommended to undergo the examination when you have an ongoing urinary tract infection, as the values that can be found may be altered.
Normal values of PSA
In general, i normal values of total PSA in the blood must be less than 4 ng / ml. However, it should be remembered that the physiological levels of this protein vary according to the age of the patient:
- Less than 40 years = less than or equal to 2 ng / ml
- 40 - 49 years = less than or equal to 2.5 ng / ml
- 50 - 59 years = less than or equal to 3.5 ng / ml
- 60 - 69 years = less than or equal to 4.5 ng / ml
- 70 - 79 years = less than or equal to 6.5 ng / ml
- Over 80 years = less than or equal to 7.2 ng / mL
PSA free and total, meaning and relationship
In addition to the PSA dosage, other parameters are also evaluated, including the ratio, which is called the PSA ratio, between PSA free and PSA bound to transport proteins in the blood. In the event that increased values of the glycoprotein are found, the doctor needs to understand what is the underlying cause of this increase. High free PSA values are more frequently associated with benign conditions, such as benign prostatic hypertrophy; increased values of PSA bound to plasma proteins are associated, however, with malignant conditions, such as tumors and carcinomas of the prostate.
What it means to have a high PSA? In general, between 4 and 10 ng / ml, the risk of disease affecting the prostate alone is increased (about 25%), but there is no close correlation between the levels found and the disease rate. If the values exceed 10 ng / ml, the association between PSA levels and the probabilities of prostate cancer confined to the organ are always stronger (they increase up to 50%). In any case, the determination of the PSA ratio follows upon finding a high PSA value in two consecutive samples, to try to understand what is the probable cause that explains the increase in the parameter. We can find:
- low free PSA / total PSA ratio (less than 0.20) = high risk of malignant prostate cancer (prostate cancer) at the base of the high PSA values found;
- normal or elevated free PSA / total PSA ratio (greater than 0.20) = low risk of having a malignant disease as the cause of the PSA increase.
PSA values after prostatectomy (surgery to completely remove the organ) must therefore be less than 0.2 ng / ml within one month. However, it must be emphasized that the measurement of total blood PSA is not a perfectly diagnostic test, as the presence of pathologies is not uncommon even with PSA values normal or below the pathological limit: until a few years ago, PSA was considered a tumor marker for the diagnosis of prostatic neoplastic pathology, while today its role has been downsized to a simple screening exam for prostate health.
The finding, therefore, of a single high PSA value is not considered sufficient to be able to diagnose cancer. It will therefore be the task of the urologist to always carefully evaluate the results obtained from the sampling, in order to be able to recommend other tests or in-depth examinations if he deems it necessary: first of all, the doctor must find a persistence of the high values even at a second blood sampling .
Should this occur, they will be able to follow a prostate biopsy, specific imaging tests (such as ultrasound, CT and MRI) and other more specific laboratory tests which may be chosen based on the doctor's diagnostic hypothesis and on the basis of his experience with the field.
Causes of high PSA
In general, therefore, those blood values above 4 ng / ml are considered high. The main causes of high total PSA are prostatic diseases, such as:
- prostate cancer (in which more frequently there is a high PSA value associated with a low ratio of free PSA to plasma protein bound PSA)
- benign prostatic hypertrophy (in which total PSA peaks are even higher than those found in neoplastic pathologies, associated with a ratio between free PSA and PSA bound to high proteins);
- some inflammations or infections of the prostate (or prostatitis): we can more easily find increased values in case of chronic bacterial prostatitis (type II prostatitis) and in case of chronic pelvic pain syndromes (type III prostatitis);
- conditions of ischemia or infarction of the prostate.
Beyond that, among the causes of high PSA, we can also have non-prostatic diseases, such as:
- urinary infections (this is why it is not necessary to take the sample in case of concomitance with this pathology);
- acute urinary retentions;
- erectile dysfunction.
In addition to these reasons, we can also find others that are not directly related to the expression of an underlying pathology:
- aging (it is enough to see how the values that are considered normal increase as the age of the subject under examination increases);
- following surgery or some maneuvers (such as rectal exploration) at the level of the prostate;
- following anything related to organ trauma due to prostate examination or diagnostic tests (insertion of a catheter, rectoscopy, colonoscopy, cystoscopy or prostatic biopsy);
- following chronic injuries to the prostate (prolonged use of bicycles or motor vehicles, horseback riding, etc.);
- following recent sexual intercourse ended with ejaculation.
Furthermore, an elevation of the PSA can rarely be found in neoplastic pathologies in locations other than the prostate. Among the most commonly associated with this increase in value, we find:
- colon cancer;
- liver cancer;
- lung cancer;
- breast cancer;
- kidney cancer.
High PSA Symptoms
The symptomatology associated with a more frequent finding of increased PSA is linked primarily to pathological processes related to the prostate. The most common high PSA symptoms that should sound like a wake-up call are:
- difficulty urinating;
- presence of weak and slow flow of urine when urinating;
- urinary leakage at the end of urination;
- increased frequency of urination daily, especially during the night;
- feeling of urgent need to urinate, though
- sensation of incomplete bladder emptying;
- presence of visible blood in urine or semen;
- burning sensation when urinating;
- reduced sexual desire and libido;
- painful ejaculation.
Low PSA: causes and symptoms
On exams, however, the PSA may be very low. A low PSA is frequently associated with:
- significant obesity of the patient under examination (this relationship was recently discovered, although to date there are no clear explanations for this phenomenon);
- taking medications for prostatic hypertrophy (such as 5-alpha-reductase inhibitors);
- low blood testosterone levels.
Often, there is no symptomatology reported by the patient and the finding of this value is to be considered incidental.Tags: Analysis Laboratory medicine Prostate Urology