Prostate Specific Antigen

Prostate cancer occurs in the prostate, a gland in the male reproductive system. Read more about prostate cancer here.

Visual representation of prostrate cancer

The prostate gland produces a protein known as Prostate specific antigen (PSA). The PSA test is recommended as a part of regular periodic checkups. However, it is particularly advised for people who are at a higher risk of developing prostate cancer.

What is PSA?

The PSA is produced by both normal and malignant cells. The test determines the levels of PSA in the blood. The levels are depicted in nanograms per milliliter (ng/mL). Elevated levels of PSA might indicate prostate cancer or benign conditions. This test is used to detect cancer if the patients show any symptoms or when prostate cancer is suspected during digital rectal examinations. The test is carried out by taking the patient’s blood sample and measuring its PSA levels.
Apart from prostate cancer, benign conditions like inflammation and enlargement of the prostate also cause elevated PSA levels. It is also possible that patients experiencing both cancerous and benign tumours to have higher PSA levels.

When do men need PSA tests:

Men with an average risk of developing prostate cancer are recommended to take the PSA test once in every 2 years. Most men above 55 years are advised to take the test after talking to the doctors about the benefits, risks and limitations of there PSA test.

  • PSA tests are not recommended for men below 40 years.
  • Very regular screening is not recommended for men between 40 and 54 years age group with an average risk of developing the cancer.
  • After talking to the doctor regarding the pros and cons of PSA screening along with the risk factors of prostate cancer, men are recommended a screening for every 2 years. Yearly screenings are not advised to avoid overdiagnosis.
  • PSA screening is not recommended for men over 70 years who have a life expectancy lesser than 10 to 15 years.

Read more about risk factors of prostate cancer here.

Factors that influence the PSA levels in the body:


Patients who experience problems in the prostate gland are at an increased risk of higher PSA levels. The PSA in the body generally increases with age.


Medical history of the patient plays a keen role in variating the PSA levels in the body, which is why the patients have to give all their medical details to the doctor before PSA screening. Drugs like finasteride and dutasteride used for benign prostate hyperplasia lower the PSA levels almost by half.

PSA test results:

The normal levels of PSA in the body varies for each man. It changes with time in all men. Previously, 4.0 ng/mL of PSA was considered abnormal. But, in recent times, patients with lower PSA levels have been diagnosed with prostate cancer, while those with higher PSA levels do not have prostate cancer. This has lead to a conclusion that there is no specific normal or abnormal level of PSA in the blood.
On a generalized basis, extreme high PSA levels in the blood or a steady rise in the PSA levels indicate prostate cancer or benign conditions.

PSA screening after prostate cancer treatments:

Patients who have been treated for prostate cancer are at a higher risk of developing recurrent prostate cancer, which might increase the PSA levels in the blood. This condition is referred as biochemical relapse.
Hence, PSA test of prostate cancer is often used to monitor recurrence. However, the PSA levels alone do not alone confirm recurrent prostate cancer. Various other factors and diagnostic tests are performed to recommend further treatment. Read more about treatment options for prostate cancer here.

Alternative PSA tests:

Before recommending biopsy and other diagnostic tests to confirm the prostate cancer, new types of PSA tests are used to measure the PSA levels in the blood to more precisity. These are often a part of diagnosis which involved checking the PSA levels in the blood to confirm prostate cancer. Read more about diagnosis of prostate cancer here.

Percent-free PSA test:

This blood test involves taking two major forms of PSA in blood. One which is bound to the blood proteins and the other which circulates freely in the body. This test determines the comparison between the total PSA and the PSA that circulates freely. Prostate cancer lowers the free PSA levels in the body. Patients having a borderline PSA and low percent-free PSA are at 50% higher risk of having prostate cancer.

PSA velocity:

PSA velocity is the change in PSA levels with time. A steady increase greater than 0.75 ng/mL shows a higher risk of having prostate cancer.

Urine PCA3 test:

This test determines the fusion of genes that is present in 50% men with prostate cancer who have been tested for PSA levels. It is performed to decide if the patient requires a biopsy or not.

Limitations of PSA test for prostate cancer:

Following are the limitations that PSA test could affect the diagnosis of a patient:

  • PSA tests doesn’t not reduce the cancer
  • PSA tests cannot detect early stages of prostate cancer
  • PSA tests might give false-positive and false-negative results

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