Free PSA: the norms, indications for the analysis of how to take

Scientific editor: M. Merkusheva, PSPbGMU them. Acad. Pavlov, general medicine.
March, 2019.

Synonyms: Free PSA, prostate specific antigen free, fPSA, Prostate-specific antigen free, f-PSA.

Free prostate specific antigen (PSA) is an important marker for the determination of benign and malignant tumors of the prostate. The study is to determine the ratio overall and the free form of this component that makes it possible to evaluate the risks of the forecasts and of a prostate disease.

Overview

PSA is a glycoprotein (a protein). It is produced prostatic ductal epithelium produces enzymatic effect, providing the required viscosity ejaculate.

PSA can be detected in healthy tissue of the prostate as well as in diseased cells with altered adenoma, cancer, polyps, cysts, hyperplasia, etc. It is also detected in prostatic secretions, seminal fluid, blood. The ejaculate contains mainly free PSA, in a concentration of 1 million ng / ml¹.

Following production by epithelial cells, prostate specific antigen released into the bloodstream where circulates in two states: the bound and unbound. The half-life of 4 days PSA. The protein can bind to antiproteases (alpha-1-antichymotrypsin) and other proteins (bound form). The share of the free PSA in serum is an average of 10%. Free and bound fractions make up total PSA. The concentration of total PSA is normal can be increased at the age of patients, but it should not exceed 4.6 ng / ml.

For suspected benign or malignant tumors in the prostate is estimated index or the ratio between the total and the free form of PSA (free to total). The need for this study is increased in the case where a preliminary analysis showed total PSA values ​​in the range of more than 4 ng / ml.

On a note: in benign development process (hyperplasia prostate tissue) and increasing PSA index is 15% or higher. Also, this figure depends on the age of the patient - in older men the index tends to decrease.

Increased total or free PSA in serum is often indicative of the progression of the tumor process or the ineffectiveness of the chosen treatment regimen. Sustained reduction in PSA levels over time indicates remission, good forecasts and the positive outcome of therapy.

Indications for the determination of free PSA

• Most often, a free PSA test is assigned to clarify the results of the study on total PSAWhen the last value of more than 4 ng / ml.
• To address the issue of the need for prostate biopsy (analysis assigned in conjunction with digital rectal examination).
• For differential diagnosis benign prostatic hyperplasia and prostate cancer.

Other indications for the test are as follows:

• patient age older than 50 years;
• 40 years - family history (first-degree relative suffering from malignant neoplasms of the pelvic organs);
• prostate hyperplasia tissue according to ultrasound or rectal examination;
• the presence of symptoms characteristic of benign or malignant prostate processes (erectile dysfunction, perineal pain, decreased libido, impaired micturition, etc...);
• monitoring the effectiveness of therapy is already diagnosed with prostate pathology, identification of metastasis risk of remission or relapse;
• selection regimen prostatic carcinoma;
• patient monitoring state after removal of the prostate tumor (relapse prophylaxis);
• Assessment of patients with prostatic hypertrophy (early diagnosis of carcinoma);
• checkup (optional).

Interpretation of the results of the analysis carried out on the free PSA narrow specialists: oncologist, internist, surgeon, urologist, andrologist.

Free PSA is normal

Important! Rates can vary depending on the reagents and equipment used in a particular laboratory. That is why the interpretation of results it is necessary to use standards adopted in that laboratory, where medical tests. It is also necessary to pay attention to the units.

A common unit of measurement for the test are selected ng / ml.

Determining the level of its clinically impractical without measurement total PSA and calculating the ratio therebetween. Index is defined by the formula:

free PSA / total PSA * 100%

The result is evaluated as follows:

when the total PSA level of 4-10 ng / ml and a negative result of digital rectal examination²

• below 10% - high risk cancer process - prostate cancer;

• more than 25% - of benign hyperplasia (tissue growth) of the prostate, lower risk of prostate cancer.

The proportion of free PSA in prostate cancer is much lower in comparison with its level in benign process.

In patients with prostate cancer in the blood is determined by the longer bound PSA than free. And in patients with benign prostatic hyperplasia vice versa.

Important! Interpretation of the results is always carried out comprehensively. An accurate diagnosis on the basis of only one analysis impossible.

What can cause a false positive result

Important! A slight increase in the concentration of prostate specific antigen can be observed for 20 days after prostatectomy, prostatic massage, or tissue biopsy.

• Medications. Previously it was thought that the false-positive results can be triggered by drugs designed for the treatment of benign prostatic hyperplasia. However, recent studies have refuted this claim in part - of the free PSA level does not depend on receiving finasteride and dutasteride (preparations for treating benign prostatic hyperplasia gland)³.
• Heterophile antibodies. They may be present in blood samples of patients receiving therapy with monoclonal antibodies. As they are discovered during the diagnostic procedures with the use of immunoglobulins. In rare cases, these antibodies detected in patients who have regular contact with animals.
• Total PSA in serum. If it exceeds the permissible physiological level, there may be interference in the direction of increasing the results of free PSA.
• Medical manipulation. Enhance the value of research, including massage and palpation of the prostate biopsy, X-ray, ultrasound transrectal prostate MRI, etc...
• Failure to comply with the rules of preparation for the test, including ejaculation on the eve of the meeting, also give a false positive result. (Free PSA returns to normal after 6 hours after ejaculation).
• Cystoscopy, bladder catheterization
• urinary tract infections, sexually transmitted infections by
• Intense cycling.

In order to eliminate false results study levels of total and free PSA fractions and their ratio is carried out the same method and from the same batch of serum. It is therefore advisable to monitor the dynamics within the same laboratory using the same reagents.

Features of preparation for analysis

Material for the study: serum of venous blood.

Method biomaterial sampling: the antecubital vein venipuncture.

The recommended duration of treatment: morning (until 11.00).

Mandatory training requirements: strict fasting!

Additionally:

• eve venipuncture excluded from the diet spicy, fatty foods;
• the day before the procedure:
• limit consumption of soft drinks, alcoholic drinks, energy;
• per day to eliminate physical stress, including sex, cycling;
• exclude emotional stress (if possible);
• 2-3 hours prior to blood sampling forbidden smoking allowed to drink only water without gas.

Analysis is carried out not earlier than one week after any therapeutic and diagnostic procedures in the pelvic organs: prostate epithelial tissue biopsy (not earlier than 6 weeks), digital rectal examination, MRI with contrast, transrectal ultrasound, ergometry, colonoscopy, laser therapy, cystoscopy et al., Minimum 8 weeks after treatment prostatitis.

In the direction of the study indicate the presence of free PSA confirmed diagnosis of prostate cancer, as well as information about ongoing medical manipulations before taking the drug, and so on. D.

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sources:

• 1, 3. Stanley A Brosman, MD. Prostate-Specific Antigen Testing. - Medscape, 2015.
• 2. N. Mottet (Chair), J. Bellmunt. Guidelines on Prostate Cancer. - European Association of Urology, 2015.