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Prostate Specific Antigen (PSA) Blood Test

Last updated May 7, 2018

DoveMed.com

Microscopic pathology image showing metastatic prostate carcinoma to the bone which stains positive for Prostate Specific Antigen (PSA) on immuno stain.


What are the other Names for this Test? (Equivalent Terms)

  • Prostate Screening Test
  • PSA Blood Test

What is Prostate Specific Antigen (PSA) Blood Test? (Background Information)

  • Prostate Specific Antigen (PSA) is a protein secreted by the prostate gland. The prostate, is a gland that encircles the urethra, in males. It secretes a fluid, which forms a part of the semen
  • Most of the PSA, secreted by the prostate are released out through the semen, except a small portion that enters into the blood circulation

There are two types of Prostate Specific Antigen; free Prostate Specific Antigen and Complex Prostate Specific Antigen (PSA-bound to protein). Usually, the PSA Blood Test refers to the total Prostate Specific Antigen (both free and complex PSA).

The Prostate Specific Antigen Test is a good tool to detect prostate cancer, though not a perfect one, because PSA levels are increased with many other conditions, like benign prostate enlargement, old age, prostate infections, and with interventional procedures, like cystoscopy (a procedure used to visualize the bladder).

  • Prostate Specific Antigen Blood Test is significant only in clinically-relevant patients (i.e., in patients with symptoms of prostate cancer). Any positive test result should be followed by a rectal examination and prostate biopsy, as determined by the healthcare provider. A prostate biopsy is the gold standard in diagnosing prostate cancer
  • The goal of screening is to minimize unnecessary biopsies and to detect clinically significant prostate cancer, while it is still confined to the prostate
  • Free Prostate Specific Antigen and complex Prostate Specific Antigen (cPSA) tests may be ordered individually. These tests were developed to better differentiate between ‘cancer-related’ and ‘non-cancer related’ Prostate Specific Antigen increases. Both tests operate on the principle that men with prostate cancer, frequently have altered ratios of the two forms of PSA – decreased amounts of free Prostate Specific Antigen and increased amounts of cProstate Specific Antigen

What are the Clinical Indications for performing the Prostate Specific Antigen (PSA) Blood Test?

Prostate Specific Antigen Blood Test is used to screen for prostate cancer in men. There is no data available on the benefit of screening non-symptomatic men. PSA is used to monitor the response to treatment and recurrence in patients with prostate cancer, and to screen men with symptoms of prostate cancer. These include:

  • Increased frequency of urination, both during day and night
  • Increased urgency to pass urine, straining to pass urine
  • Passing a thin stream of urine
  • Difficulty in initiating the stream
  • A sense of incomplete emptying of the urinary bladder

There is no specific data regarding how frequently one has to be tested. It is dependent upon the condition of each individual patient, and based on the healthcare provider’s judgment.

How is the Specimen Collected for Prostate Specific Antigen (PSA) Blood Test?

Sample required: Blood

Process:Insertion of needle into a vein (arm).

Preparation required:

  • Avoid ejaculation, 24-hours prior to the test
  • The test should be done prior to a rectal examination
  • The test should be done prior to a prostate biopsy

What is the Significance of the Prostate Specific Antigen (PSA) Blood Test Result?

  • The normal value of Prostate Specific Antigen is below 4ng/dl. When the value is between 4-10ng/dl, then the chance of prostate cancer is around 25%
  • When the value is above 10ng/dl, then the chance of prostate cancer is close to 100%. In such individuals, a prostate biopsy, has to be performed following the test

In addition to the introduction of the free Prostate Specific Antigen and complex Prostate Specific Antigen tests, there have been efforts to increase the usefulness of the total Prostate Specific Antigen, as a screening tool. They include:

  • Prostate Specific Antigen velocity: This is the change in PSA concentrations over time. If PSA continues to rise significantly over time (such as over three, or more years), then it is more likely that prostate cancer is present. If it climbs rapidly, then the affected person may have a more aggressive form of the cancer
  • Prostate Specific Antigen doubling time: This is another version of the PSA velocity. It measures how rapidly the PSA concentration doubles
  • Prostate Specific Antigen density: It is a comparison of the PSA concentration and volume of the prostate (as measured by an ultrasound). Men with larger prostates tend to produce more PSA, so this factor is an adjustment to compensate for the size
  • Age-specific Prostate Specific Antigen ranges: Since, PSA levels naturally increase as a man ages, it has been proposed that normal ranges be tailored to a man's age

In individuals already diagnosed with prostate cancer, PSA values should decrease with treatment.If concentrations do not fall to very low levels, then the treatment has not been fully effective.

Following treatment, the Prostate Specific Antigen Blood Test is performed at regular intervals to monitor for any cancer recurrence. Since, even tiny increases can be significant, those affected may want to have their ‘monitoring’ PSA Tests done by the same laboratory each time, so that testing variation is kept to a minimum.

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Rigorous physical activity affecting the prostate, such as bicycle riding, may cause a temporary elevation in Prostate Specific Antigen levels
  • Large doses of some chemotherapeutic drugs, such as cyclophosphamide and methotrexate, may increase or decrease PSA levels
  • In some men, Prostate Specific Antigen may rise temporarily due to other prostate conditions, especially an infection. A recent study found that in about half of the men with high PSA, the values later return to normal. Some authorities recommend that in case of a high PSA, the test should be repeated, between 6 weeks to 3 months, before taking any further action. Some physicians may even prescribe a course of antibiotics, if there is evidence of a prostate infection
  • Not all cases of prostate cancer cause an increase in Prostate Specific Antigen levels. In a few individuals, the prostate cancer may not secrete PSA, and hence PSA levels may be normal. This scenario occurs rarely and your healthcare provider may perform a prostate biopsy, if the level of suspicion of prostate cancer, is high

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 11, 2013
Last updated: May 7, 2018