Letters
General medicine Surgery
Volume 186 - Issue 7

Clinical paradigms revisited

Author:  Richard M Mendelson

Med J Aust 2007; 186 (7): 381-383. || doi: 10.5694/j.1326-5377.2007.tb00950.x
Published online: 2 April 2007
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To the Editor: Like Schattner, I am appalled by the attitude to diagnosis displayed by Wong regarding the use of computed tomography (CT) scanning in preference to initial history-taking and physical examination in abdominal pain.1 Unfortunately, this approach is becoming increasingly more prevalent among junior staff (and even among some senior staff).

Wong poses the question, “[W]hy do some clinicians continue to routinely promulgate the sacred and arcane ritual of taking a history and doing an examination, which, as diagnostic tools, are clearly second-rate?” There are several reasons why I continue to promulgate the classical paradigm.

Firstly, I would remind him of Bayes’ theorem: post-test probability equals pre-test probability multiplied by the likelihood ratio of the test. Put simply, this means that, for a test that is not 100% accurate (ie, effectively, all imaging tests), you cannot interpret the meaning of the result without having some idea of the pre-test probability of a diagnosis. And how can you satisfactorily arrive at a pre-test probability without having clinically assessed the patient? In addition, the radiologist is able to interpret the images more accurately when there are clinical details provided.2

Secondly, is Wong seriously suggesting that all patients with abdominal pain, including young adults and children, undergo CT scanning without any kind of clinical filtering or assessment? This is wrong and potentially negligent. The radiation dose received by the patient from an abdominal CT scan is a serious consideration. Assuming a total effective body dose of 10 mSv, there is an excess risk of a radiation-induced fatal cancer of about 1 in 2000.3 Apart from the risk to the individual, the number of iatrogenic cancers potentially induced in the community by indiscriminate use of CT would be a major concern.4

Thirdly, the implication of Wong’s letter is that clinical assessment and imaging are somehow in competition with each other, whereas nothing could be further from the truth. Of course, modern imaging has contributed to making diagnosis far more accurate than in the time of Hippocrates, but a complementary approach is far more rewarding for patients and doctors.

Lastly, in patients with abdominal pain, there are many occasions when no imaging is required and others when ultrasonography is more appropriate than CT, because it avoids ionising radiation in young patients and is more accurate for diagnosing gynaecological causes of pain.5

Author

  • Richard M Mendelson1
  • 1. Department of Diagnostic and Interventional Radiology, Royal Perth Hospital, Perth, WA.

Correspondence: richard.mendelson@health.wa.gov.au

References

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