Essential Facts: Prostate-specific antigen

VOL: 102, ISSUE: 42, PAGE NO: 41

Rachel Gilbert, BSc, DipHE, RN

care services manager for BUPA Care Homes and at the time of writing was continence nurse specialist, Kingston Primary Care Trust

Prostate-specific antigen (PSA) is a glycoprotein produced by the prostate gland and is responsible for liquefying semen.

Prostate-specific antigen (PSA) is a glycoprotein produced by the prostate gland and is responsible for liquefying semen.

Levels of PSA in the blood can become raised by cancer cells, prostatitis, benign prostate enlargement, urinary retention, urethral catheters, rectal penetration, recent prostate surgery, drugs such as finasteride, prolonged exercise and ejaculation.

A normal PSA reading is usually recorded as <4.0ng/ml. However, it is difficult to define the 'normal' range since PSA usually rises with age. The age-specific cut-off measurements recommended by the Prostate Cancer Risk Management Programme (www.cancerscreening.nhs.uk/prostate/prostate-booklet-text.pdf) are:

• Aged 50-59 years &ge;3.0ng/ml;
• Aged 60-69 years &ge;4.0ng/ml;
• Aged 70 years and older >5.0ng/ml.

There are no age-specific reference PSA ranges provided for men aged over 80 years because nearly all men of this age have a focus of cancer in the prostate.

PSA level is not a reliable indicator of prostate cancer. It will not indicate if any cancer present is slow or fast growing or how advanced it is. As a result men in the UK are not routinely offered PSA testing.

The PSA blood test

Up to 20% of men with clinically significant prostate cancer will have a normal PSA level and approximately two-thirds of those with an elevated PSA do not have prostate cancer. The PSA test is therefore not diagnostic, although prostate cancer is more likely with raised levels of PSA. A PSA test result should be considered only as part of patient assessment and may support the need for further investigation.

• PSA normal - prostate cancer is unlikely if no other symptoms are present. No further action is usually required;
• PSA slightly raised - prostate cancer probably not present, but further investigation may be necessary;
• PSA significantly raised - urological referral for transrectal ultrasound/biopsy.

Due to the possible outcome and implications of PSA testing, patients should be provided with adequate information before consent for the blood sample is obtained.