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Prostate Specific Antigen (Free) PSA

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Interpreting Results
Prostate Specific Antigen (Free) PSA

Overview of Prostate Specific Antigen (Free) PSA

What is Prostate Specific Antigen (Free) PSA?

Prostate Specific Antigen or PSA is a protein secreted by the prostate gland which serves as a marker for conditions affecting the prostate gland including prostate cancer, Benign Prostatic Hyperplasia (BPH), and prostatitis (inflammation of the prostate gland). The PSA (Free) Test is performed to measure the levels of unbound or free PSA in blood.

Why is Prostate Specific Antigen (Free) PSA done?

The PSA (Free) Test is performed:

·      To identify the need for Prostate biopsy in patients with increased PSA (Total) levels

·   To differentiate between Prostate cancer and other benign conditions of the Prostate gland like BPH

What does Prostate Specific Antigen (Free) PSA Measure?

The PSA (Free) Test measures the levels of unbound or free PSA in blood.

PSA is a protein which is secreted by the prostate gland. The prostate gland is a male accessory reproductive organ, the secretion of which contributes to the formation of the seminal fluid. Most of the PSA produced is secreted in the seminal fluid along with other prostatic secretions and only a small amount is secreted into the bloodstream. PSA is considered to be a tumor marker since its levels in the blood are elevated in prostate cancer and BPH, and it is used as a preliminary screening test before further diagnostic procedures.

PSA in blood is found as either complexed PSA (bound to other proteins) or free PSA. The PSA Test usually calculates the total PSA levels in the blood including both free and complexed forms, whereas the PSA (Free) test measures the levels of unbound or free PSA in blood.

Some doctors prefer to measure free PSA in patients with a total PSA level between 4 ng/ml and 10 ng/ml rather than subjecting everyone with an elevated PSA to a biopsy as it is an invasive procedure.

Preparation for Prostate Specific Antigen (Free) PSA

  • The sample should be collected before a digital rectal examination or rectal prostatic ultrasonography is performed and before or several days after the prostate biopsy.

Sample Type for Prostate Specific Antigen (Free) PSA

The sample type collected for Prostate Specific Antigen (Free) PSA is: Blood

Interpreting Prostate Specific Antigen (Free) PSA results


The normal value of PSA (total) in blood is below 4.0 ng/ml

Total PSA levels roughly between 4.0 and 10.0 ng/ml are considered in “grey zone” and the probability of finding prostate cancer based on % free PSA in such cases is given below:

% free PSA

   Probability of prostate cancer









Greater than 25%


Some patients with a “normal” total PSA may have cancer. So, some doctors order both tests at the same time as a low total PSA and a low percentage of free PSA would probably indicates biopsy in these cases.

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Prostate Specific Antigen (Free) PSA

Frequently Asked Questions about Prostate Specific Antigen (Free) PSA

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood sample from a blood vessel in your arm, generally from the inner side of the elbow area. The doctor, nurse or the phlebotomist will tie an elastic band around your arm which will help the blood vessels to swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution. The needle is then inserted into the blood vessel to collect the sample. You may feel a tiny pinprick during the procedure. Blood sample, once collected, is then sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. Is there any preparation required before the PSA test?
Ejaculation (either during sex or masturbation) is to be avoided for 24 hours before the sample is collected. Inform the doctor of any medications you may be taking. No other specific preparations are usually required before the PSA Test.
Q. What factors can affect the test results?
The PSA levels in the blood can be affected by a number of factors including: · Ejaculation · Direct prostate examinations · Physical activities like cycling, horse-riding, etc. · Chemotherapy · Infections of the prostate gland · Prostate Biopsy · Cystoscopy (a procedure where an endoscope is inserted through the urethra to examine the urinary bladder) · Urinary catheter · Urinary tract infections
Q. What additional tests can be prescribed by your doctor in case the result of PSA test is not normal?
Additional tests that may be prescribed in case of abnormal PSA test result are: · Digital Rectal Examination (DRE) · Free PSA Test · Urinalysis · Prostate Ultrasound · Prostate Biopsy
Q. What other ways are the PSA test results evaluated to help in diagnosis?
PSA Test results can also be evaluated in the following ways: · PSA Velocity: Estimates increase or decrease in PSA levels over time. A significant increase indicates cancer. Faster the increase in PSA, more aggressive is the cancer. · PSA Doubling Time: Also tracks PSA increase by measuring the time in which PSA levels double. · PSA Density: Measures PSA levels in blood against volume of the prostate gland seen by ultrasound. Greater PSA levels than expected for the visible volume of prostate indicate chance of cancer. · Age-specific PSA: PSA levels increase with age, hence the normal range of PSA is to be established for the age of the particular person being tested.
Q. What is BPH?
Benign Prostatic Hyperplasia or BPH is a condition characterized by enlargement of the prostate gland. Enlargement due to BPH is usually caused due to aging and does not develop into cancer. The enlarged prostate puts pressure on the urethra and leads to blockage, causing urinary retention, weak or no urine flow, urinary bladder stones, infections or kidney damage.
Q. Can the PSA test detect all types of prostate cancer?
Increased PSA level is usually an indication of prostate cancer. However, it cannot confirm the diagnosis of cancer since elevated PSA levels can be seen in other conditions as well. Also, PSA levels are not significantly increased in slow growing forms of prostate cancer and many times prostate cancer can occur without increased PSA levels. PSA is usually accompanied by other tests like Digital Rectal Examination and biopsy to confirm the diagnosis of cancer.
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