CLINICAL UPDATE
PSA screening, in context
PSA has become an acronym that provokes strong responses. Essentially, men who are not suitable for consideration of curative intent treatment should not be screened. Men whose screening is positive need appropriate referral so the patient is not faced with a situation where delay has culminated in incurable disease. This may have profound medicolegal consequences for the referring Doctor.
PSA’ s strengths and weaknesses
PSA screening needs to be considered in context, like any other test. With regard to prostate cancer it has a sensitivity(~ 21 % for detecting any cancer at a PSA cut-off of 4ng / mL), a specificity(~ 91 % for a PSA cut-off of 4.0 ng / mL), a positive predictive value(~ 30 % for a PSA > 4ng / mL) and a negative predictive value(~ 85 % for a PSA ≤4 ng / mL).
While prostate cancer can be diagnosed at any level of PSA, concluding that“ PSA testing can’ t detect prostate cancer”( as the discoverer of PSA Richard Ablin stated in an oft quoted 2010 op-ed in the New York Times) is to throw the baby out with the bath-water.
Despite its limitations, it remains overwhelmingly the best prostate cancer tumour marker that we have.
US & Australian recommendations
PSA screening for cancer is contentious. The American Urological Association( AUA) has just issued revised guidelines that should be considered alongside the Urological Society of Australia and New Zealand( USANZ) recommendations:
�� �������������������������������
�� ���������������������������������������� screening between ages 40-54 only in those at higher risk( e. g. positive family history or African-American race), and according to patient-doctor wishes.
�� ������������������������������������ significant predictor of later prostate cancer and disease-specific outcomes. USANZ recommend men interested in their prostate health have a single PSA test and digital rectal examination( DRE) at or beyond age 40, to help estimate prostate cancer risk over the next 10-20 years. In these circumstances PSA is considered as providing prostate cancer risk stratification rather than true screening. If the result is less than the age specific median, the intensity of surveillance may be reduced but those with PSA levels above should be more carefully monitored.
�� ������������������������������������� in men aged 55-69; both the AUA and USANZ recommends doctor-patient shared decision-making based on a man ' s values and preferences.
�� ����������������������������������������� years( or less often) may be preferred over annual screening, to preserve most benefits reduced by false positives; rescreening intervals can be individualised according to a baseline PSA level.
Dr Robert Davies, Urologist,
West Australian
Urologic Research Organisation. Tel 9381 8945
�� ����������������������������������� PSA screening over age 70 or in any man with < 10-15 year life expectancy( although some over age 70 and in excellent health may benefit).
In short, PSA screening should be confined to men who are most likely to benefit from early diagnosis and treatment.
Act on screening results
PSAs appropriately performed in a man suitable for curative intent treatment, should be acted on. Whilst repeating an isolated elevated PSA after a few months is a reasonable first course of action, watching serial PSAs gradually progress from minimally to exceedingly elevated over several years is akin to allowing a patient to gradually exsanguinate whilst dutifully measuring a rising pulse and falling blood pressure.
Since the risk of extra prostatic spread increases continuously as PSA rises, early referral can mean the difference between detection of localised( curable) versus locally advanced or metastatic( incurable) disease. The proportion of organ-confined cancers drops to < 50 % for PSA values > 10ng / mL.
��Performing high dose rate prostatic brachytherapy at SCGH.
Rectal examination
PSA has not replaced digital rectal examination( DRE) – both should be performed as part of screening, as in combination, the positive predictive value doubles when the PSA is in the 4-10ng / mL range. Furthermore, the risk of missing a significant high grade cancer by omitting the DRE has been estimated at 17 % in one major study.
Author competing interests: No relevant disclosures.
Medicolegal
Stray Tests
Q“ Three
patients have recently asked me to order tests for them, after non-medicos requested this. One wanted an antenatal screen and had no intention of attending any medico or midwife for pregnancy care. One suggested we do a PSA, which I
Ms Morag Smith, Avant’ s Senior Solicitor, answers the question for Medical Forum.
disagreed with. The other wanted a re-test of her thyroid, which her naturopath said was warranted and cheaper under Medicare. Where do I stand, in a medicolegal sense?”
APatients who insist on seeing a non-medical person for follow up and treatment should be informed of the risks of obtaining treatment from someone who is not a doctor. The discussion should involve taking steps to ascertain the patient’ s understanding of their condition and reasons for, and the nature of, treatment. If, despite counselling, the patient continues to refuse to see you for follow up, you may want to consider whether to end the doctor-patient relationship due to the patient’ s failure to follow your advice and recommendations. Details of the discussion should be documented in the patient’ s file. You should only agree to a test or investigation requested by a non-medical third party if you believe it is clinically indicated. Should you agree to conduct a test or investigation, you still need to take a history and examine the patient to confirm that the test is clinically indicated. In addition, you still owe a duty to the patient to inform them of any finding that requires follow up. This duty applies even if the patient states they do not intend returning to see you to discuss the results. If a patient requests a test or investigation and you do not agree that the test / investigation is required, it is not advisable to comply with the patient’ s request. Medicare pays for clinically-relevant services. This means services that are generally accepted by your peers as being necessary for the appropriate treatment of the patient. If you order a test that is not clinically relevant, you risk a possible review by the Department of Human Services. It is also possible that you could face disciplinary proceedings.
Finally, you can always contact your MDO for advice on managing situations such as this. �
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