What is PSA?

PSA (prostate specific antigen) is a protein secreted by cells of the prostate gland and is found in the order of a few milligrams in seminal fluid. The role of this protein is the liquefaction of sperm.


A tiny fraction of this protein passes through the blood (a few nanograms) and can thus be measured by a simple blood sample.


PSA occurs in different forms in the blood, either in free form (30%) or in so-called complexed form, linked to other blood proteins (70%). The total PSA assay includes these two free and complexed forms.



Biological analysis laboratories use kites for assaying total PSA, in the free form or in the complexed form (less often requested). The ratio of free PSA to total PSA (PSA L / T) decreases in prostate cancer and can also be calculated.

What kind of PSA?

Apart from some special circumstances, your doctor is recommended not to prescribe the first-line dosage of free PSA or complexed PSA because of dosing errors and more frequent false positives or negatives of free PSA.


The blood dosage of total PSA is sufficient in the vast majority of cases and particularly after surgical, medical or radiotherapy treatment. The assay of free PSA is quite unnecessary.

What is normal PSA value?

The most widely used cut-off value for PSA is 4 ng / ml. But a single dosage is not enough because there may be an individual variability of plus or minus 30% between 2 dosages.


PSA can increase in prostate cancer. However, a number of factors unrelated to cancer can also affect its value. Like prostate volume in benign prostatic hypertrophy called BPH, chronic inflammation of the prostate, or acute infection called prostatitis.



Patients on 5 alpha reductase inhibitors (Finasteride, Dutasteride), prescribed for treatment of BPH, must double the PSA value because its drugs lower the PSA value by 50% after 6 months of treatment.

How doctor interpret the value of your PSA?

The first dosage of PSA is conventionally requested only from the age of 50 and it is not requested after the age of 75. However, in patients with a family history of prostate cancer, this dosage may be prescribed earlier around the age of 45.


For a good interpretation of the result your doctor will:


Compare the value of a total PSA with the previous assays. What is called, the kinetics of PSA.

Make sure that the measurements have been taken with the same assay kits.

Check the absence of signs of prostate infection in the 3 months preceding the PSA test.

Note any medication likely to modify the PSA value.

Take into account your age, the data of the clinical examination and your associated pathologies and interpret the value of the PSA according to the volume of the prostate, possibly calculating the density of the PSA.

When Should You Really Be Worried?

Changing your PSA value is a warning but does not mean you have prostate cancer. The risk of discovering cancer is higher or lower depending on whether the examination of the prostate is abnormal, whether the progression of the PSA is confirmed, whether it is not related to a urinary tract infection or to an increase in the volume of the prostate. prostate as part of a benign hypertrophy.


The diagnosis of prostate cancer is necessarily based on prostate samples or biopsies.


The decision to perform these biopsies is made with your urologist on a set of arguments, the existence of a family history of prostate cancer, your age, your state of health, the data of the examination of the prostate by touch. rectal, prostate volume, PSA kinetics, or the results of other examinations that your urologist deems useful and anyway after having informed you of the objectives, modalities and consequences associated with these biopsies.


If the biopsies are positive, the different treatment or monitoring options can only be fully discussed after carrying out an additional assessment.

How are prostate biopsies performed?

Biopsies involve taking fragments of the prostate to look for cancer cells. This examination is the only way to make the diagnosis of prostate cancer and does not in any way promote a worsening of the disease.


Biopsies are usually performed under local anesthesia and in some cases under general anesthesia. Taking antibiotics before the biopsy (antibiotic prophylaxis) is recommended and essential to avoid the risk of infection associated with taking rectal prostate samples.


The prostate is located with an endorectal ultrasound probe.


The samples taken using a fine needle are distributed in the prostate according to a validated protocol, most often 12 samples (an MRI could be requested to direct other samples) and they are sent for examination under a microscope by a pathologist.


The main complications are the presence of blood in the urine, in the stools and in the semen the days or weeks following the sample and are usually not serious.


The risk of prostate infection (acute prostatitis) is low. The occurrence of a fever within 48 hours after the sample requires urgent medical treatment by the urologist or an emergency service. Intravenous antibiotic therapy is often necessary.


The inability to urinate or urinary retention, very rare, should also prompt you to consult urgently. It requires the establishment of urinary drainage.


An appointment is made with your urologist to communicate the results of the biopsies. If a significant cancer is discovered your urologist will determine with you the course of action and will discuss the treatment (s) best suited to your situation. If the biopsies are negative your urologist will tell you according to the criteria, described above, the rhythm and the methods of your urological follow-up in collaboration with your doctor, which could require new prostate biopsies.