PSA or prostate specific antigen is a protein that is produced exclusively in the prostate. It is known as the tumour marker for prostate cancer, although it is not only raised as a result of tumour disease. Its main limitation is that benign diseases such as infection or benign prostatic hyperplasia also cause it to be raised, whilst a low blood concentration does not always indicate that there is no cancer.
 
PSA determination from a blood sample can be used in several ways:

• In men who do not know if they have prostate cancer, such as for screening or diagnostic testing.
• In men who already have prostate cancer, as a specific marker or to monitor progress..

Types of PSA

PSA may exist in the blood in a free form or bound to other blood substances.

• When free form, it is known as free PSA
• When bound to other substances, it is known as bound PSA.

 
Total PSA is the sum of both forms of PSA and is what is usually measured on blood tests.
 
 

PSA levels

When used as a screening or diagnostic test, if the result is abnormal, additional tests should be performed. The higher the value obtained the higher the chance of having cancer.
 
If the PSA content in the blood is raised, the greater the chance of prostate cancer.
 

PSA 0-2 ng/mL | Cancer Percentage 1%

PSA 2-4 ng/mL | Cancer Percentage 15%

PSA 4-10 ng/mL | Cancer Percentage 25%

PSA >10 ng/mL | Cancer Percentage >50%

 
The value most commonly used as the upper limit of normal is 4 ng/mL (nanograms per millilitre). However, it is normal for older men to have higher concentrations as the prostate gland increases in size with age and also produces more PSA. The normal value of 4 ng/mL is perhaps too high for young men
 
The probability increases dramatically above 10 ng/mL, so it is advisable to monitor progress.
 
A small percentage of prostate cancers do not produce detectable increases in blood PSA, even in advanced disease. It is therefore important not to rely solely on this laboratory test.
 
In addition to the PSA test, a digital rectal examination of the prostate is performed by a urologist. A positive rectal examination is common in advanced stage tumours.

This is the oldest and simplest screening test. It involves insertion of the index finger into the rectum to feel the prostate and detect any enlargement or abnormality that can be found on palpation