Prostate specific antigen (PSA) is a glycoprotein enzyme which is secreted by epithelial cells of the prostate. Levels of PSA rise with prostate inflammation which can be due to:
- Benign prostatic hyperplasia
- Prostate cancer
- Infection (prostatitis, UTI)
- Trauma – e.g. from digital rectal examination, sigmoidoscopy or colonoscopy or external trauma – even such as riding a bike!
The use of PSA blood tests can be controversial and advice may be conflicting. As of 2021 it is generally NOT advised screen patients for prostate cancer with regular PSA testing, instead reserving it for those with a strong family history, of symptoms of prostatic enlargement.
There is also not a specific widely accepted cut-off level for what constitutes as a ‘raised’ PSA level. PSA naturally rises with age. Typically a level of <3.5ug/L would be considered normal, but in older patients higher levels may still be acceptable (up to 9 in new aged 80+) . Tracking the pattern of the level of PSA may be more appropriate. It is also possible to test for bound vs free PSA levels in the blood. Those with a free PSA percentage of >20% are generally considered to be low risk for prostate cancer. Those with a low percentage of <10% are very high risk for prostate cancer. Levels of 10-20% are considered indeterminate.
- In prostate cancer PSA levels may be as high as 100
- A level of >10 is highly suspicious for prostate cancer and should prompt urgent referral
- PSA level that continues to rise is more suspicious for prostate cancer
When to screen
The RACGP in Australia recommends discussing a man’s individual risk before screening, and offering patients a choice of annual screening (or not) after this discussion. This advice applies to patients aged 50-69. Routine screening is not recommended.
Those with lower urinary tract symptoms (LUTS) should have thorough urological history, examination and PSA testing – this is NOT screening in these circumstances but rather investigation of abnormal symptoms.
Those with a family history of prostate cancer particularly before the age of 55 should be considered for screening.
Pros and cons of screening
For every 1000 men aged 50-69 screened for 11 years:
|WITHOUT screening||WITH screening|
|5 men will die from prostate cancer||4 will die from prostate cancer, one possibly will be saved|
|190 will die from other causes||190 will die form other causes|
|55 men will be alive with symptomatic prostate cancer||55 men will be alive with symptomatic prostate cancer|
|87 will have a false positive PSA discovered upon biopsy of prostate|
|28 will require health care or hospitalisation for side effects of the biopsy|
|25 will have unnecessary treatment for prostate cancer|
|10 men will have incontinence or erectile dysfunction or a bowel complication as a result of the biopsy|
|1 in 2000 will die from MI as a result of unnecessary treatment or other complication|
As demonstrated above, the benefits are not clear. In my clinical experience, most men decide against prostate screening when presented with this information. The RACGP provides a handout for patients with this and more information to assist in helping them to make an informed decision. PSA screening is a good example of shared decision making between doctor and patient in modern medical practice.
When PSA is raised
Repeat the test in two weeks with free and bound PSA levels.
Consider a prostate examination (DRE – digital rectal examination) if levels of PSA remain raised.
When examining the prostate:
- Normal prostate – quite firm but a bit squidgy. About 2-3 fingers width. Symmetrical with a little dip in the middle.
- Enlarged prostate – still symmetrical – pretty much identical to normal prostate, but enlarged equally in all proportions.
- Suspicious nodule – not as symmetrical as normal. Has a hardened nodule on it
- Large, irregular prostate – large prostate, very hard and many nodules. Very high likely hood of malignancy
Consider the causes of raised PSA
- Typically remains raised for 6-8 weeks following infection
- Consider repeating test with free and bound PSA in several weeks or months
- Consider referral to urology
- Those with highly elevated PSA, or suspicious prostate on examination, or new onset LUTS or any combination of the above should be referred to urology
- Take a thorough urological history
- Lower urinary tract symtpoms
- Frequency of urination (>2 hrs is significant)
- Getting up in the night to pass urine (>2x during the night regularly is significant)
- Sexual dysfunction
- Perineal pain or discomfort
- Potentila other reasons to be raised
- Prostatitis / UTI
- Recent procedure such as sigmoidoscopy or colonoscopy
- Lower urinary tract symtpoms
- Consider USS or urinary tract – may (not always) be able to give estimate of size of prostate
- This may also be used to estimate pre and post-void volumes to assess for urinary retention
- MRI is the most accurate prostate imaging test but is not recommended to be requested in general practice, and only after urological assessment
- Abnormal Laboratory results – Prostate Specific Antigen – NPS medicinewise
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy