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Best use of PSA testing

Clinical biochemist Dr Brona Roberts uses a primary care case history to discuss how and when to order a PSA and what to discuss with patients

Clinical biochemist Dr Brona Roberts uses a primary care case history to discuss how and when to order a PSA and what to discuss with patients

The case

An otherwise fit 70-year-old male returns to see you for the results of his PSA test.

He had presented two weeks ago with a six-month history of lower urinary tract symptoms. He is otherwise well and is on no medication. Abdominal palpation reveals no evidence of an enlarged bladder or kidneys and rectal examination reveals a moderately swollen, benign-feeling prostate. His U&Es and eGFR are normal – but his PSA is elevated at 7.5ng/ml.

What does the PSA actually measure?

Prostate-specific antigen is a protein produced by the prostate gland. Small amounts of this protein leak into the bloodstream even in healthy men, but if the prostate is enlarged or diseased, the serum level is generally higher.

What does the degree of elevation tell the clinician?

First of all, serum PSA tends to rise with age, so your local laboratory should provide age-specific reference ranges to help you judge the extent of the abnormality. Then, as with many biochemical tests, the degree of the abnormality reflects the likelihood that there is an underlying disease, and the severity of the possible disease. Minor increases, such as in this case, may be due to cancer, but may also be the result of benign prostatic enlargement or infection.

How reliable is it in detecting prostate cancer?

PSA is neither very sensitive nor specific, although this depends to some degree on what is meant by ‘prostate cancer'. Half of all men in their 50s have some cancerous cells in the prostate, rising to 80% by the age of 80, but the great majority experience no significant clinical problems – far more men die with prostate cancer than from prostate cancer.

Furthermore, treatment can have highly undesirable side-effects. So ideally, the aim should not be to identify and treat every cancer, but to identify those cases in which the potential benefits of treatment outweigh the risks.

Is timing of the test important – is it affected by recent sexual activity or the rectal examination, for example?

Yes – orgasm or vigorous exertion within the previous 48 hours can elevate the PSA, and although it is appropriate to perform

a rectal exam before measuring PSA, you should leave at least a week between the examination and venepuncture. If there is a proven UTI, measurement should be delayed for a month after treatment.

With borderline elevation, as in this case, what is an appropriate management strategy?

Because of the nature of the disease and its treatments, there is no universal strategy for the investigation of prostatic symptoms, with or without raised PSA. The UK Prostate Cancer Risk Management Programme (PCRMP) has agreed some age-related referral values for PSA (see table below left) but both the PCRMP and NICE say referral should not depend on a raised PSA alone.

If you haven't already, you need to assess and discuss with this patient his risk factors for prostate cancer, which include not just PSA but also the findings on rectal exam, family history, any previous PSA measurements and race – black men are at higher risk, and Asian men at lower risk, than Caucasians.

You must also discuss the potential next step, which is prostatic biopsy, and possible treatment options if cancer is found.

He needs to know that although further testing may identify a cancer that may benefit from earlier treatment, it is not always possible to differentiate between a tumour that is destined to cause clinical disease and one that will remain silent during his lifetime.

Some treatments carry considerable risk of side-effects, including sexual dysfunction and urinary incontinence. The best evidence currently available on PSA testing in asymptomatic men suggests it can save lives – but for every death prevented, 48 other men undergo treatment.

Furthermore, carrying the label of cancer will probably cause anxiety and complicate certain other issues for him, such as obtaining health insurance.

Obviously a man's view of such risks and benefits depend considerably on his own circumstances, including any coexisting morbidity. If this is the first discussion with him, it would be wise to allow him some time to think and talk it through.

Useful information, including a leaflet for patients, is available at the NHS Cancer Screening site although strictly speaking the leaflet is designed to be read before PSA measurement.

It's entirely appropriate to refer him for biopsy, if this is his informed decision, but it may be just as appropriate to watch and wait. If he is uncertain, a repeat PSA in, say, two to three months should help – a stable level is reassuring, whereas a rise increases the likelihood of cancer being present.

Is it likely the test will be improved in the future?

In the future, laboratories may report, alongside total PSA, what percentage of this is free (uncomplexed) PSA. Low free PSA is associated with cancer. Other possible strategies for refining risk estimates include the rate of PSA rise, known as PSA velocity, or PSA doubling time.

By that stage we may also have better information on outcomes for men with various levels of PSA with and without treatment. Hopefully this will allow us to give patients more accurate information on the options.

Further information is available at guidance.nice.org.uk/CG58.

Dr Brona Roberts is a clinical biochemistry SpR at Belfast Health and Social Care Trust

Competing interests: None declared

Further reading

The Association of Clinical Biochemistry recommends the following as sources of information for GPs and patients:

Lab Tests Onlineis a general resource aimed mostly at patients to explain how tests are used in different situations

BetterTesting.org.uk is an FAQs website aimed more towards information for health professionals but may also be useful for patients seeking answers to specific testing or monitoring situations

Lab test update

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