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Evidence and Clinical Medicine
  1. M C BATESON
  1. Gastroenterologist
  2. Bishop Auckland General Hospital, UK

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    Evidence and Clinical Medicine

    (1) Evidence-Based Medicine. Two monthly journal. BMJ Publishing Group; £95 per year. (2) Clinical Evidence 3. Six monthly. BMJ Publishing Group, June 2000; £55 per year. (3)Evidence Based Gastroenterology and Hepatology. BMJ Books, 1999; £85 (ISBN 0-7279-1182-1 ).

    The practice of medicine has moved into a new phase where attempts are being made to validate medical activity more rigorously. This contrasts with the previous system of basing practice on past experience, consensus medical opinion, and the politics of the latest paper on the subject.

    It is recognised that the quality of evidence used to support ideas is variable and this is classified as:

    (A) First rate, grade A. Based on large randomised controlled trials or meta-analyses of smaller trials to achieve significance, or “all or none” cohort studies.

    (B) Adequate evidence, grade B. Based on high quality non-randomised trials, case-control studies or case series.

    (C) Contentious evidence, grade C. Medical opinion supported by ancillary studies, for example from laboratory work, or physiological and pharmacological principles.

    Evidence-Based Medicine is a two-monthly journal constructed in a format that will be familiar to fans of theReader's Digest. It is eclectic and picks out topics in a wide variety of areas, summarising the evidence and making recommendations. Each subject receives about a page. This is an accessible style but is best used as a browsing tool in the library. Most readers will find something of interest, but the majority of the contents will not be relevant to any one individual.

    Clinical Evidence is a paper covered handbook. The current issue runs to 1034 pages, so it will fit into a pocket but not leave much room for anything else. It was notionally first launched in June 1999 though the first issue only became available in the autumn. The second and third issues did come out in the right month.

    The text is grouped by major systems and though it has been reorganised for the current edition, much of the material is carried forward from the first one. Where additional material is incorporated this is indicated in the index with the word “new” in blue. Again it is not comprehensive but it does provide a very useful summary of management of conditions like myocardial infarction, prevention of malaria, and endometriosis. Junior doctors would be well advised to consult the current issue in the library. Their seniors may well prefer to own a copy themselves. Clearly the intention is that each fresh issue should supersede the previous one in the same way that theBritish National Formulary operates.

    Evidence Based Gastroenterology and Hepatology is a different animal again. A hardback book of 547 pages, it reviews the whole field of gastroenterology and hepatology fairly comprehensively. It is the kind of book that any practising gastroenterologist would like to have personally for reference. It is a sister text to Evidence Based Cardiology, and one might imagine in the future a general physician with any special interest might like to acquire a set of volumes to cover all of the major specialties, if that becomes possible.

    This is very obviously a multiauthor text. Some of the chapters are synoptic to the point of being terse, whereas the one on portal hypertension exhaustively lists the findings of papers in the text and runs to 262 references.

    Levels of evidence are indicated both in the text and boldly in the margin with As, Bs, and Cs. However, it is not always clear what this refers to in the text, nor always indeed whether the evidence accepted was that for or against a particular point.

    Two areas of specific interest that highlight the problems with evidence-based medicine are the treatment of primary biliary cirrhosis and colonoscopic surveillance in ulcerative colitis.

    At the end of the chapter on primary biliary cirrhosis one is left with the feeling that one ought to be using ursodeoxycholic acid therapy though there is no grade A evidence to support this. Indeed the Cochrane Collaboration, the Drugs & Therapeutics Bulletin, and a meta-analysis in theLancet have all poured cold water on the topic. However, the problem is that none of the trials have extended for long enough with placebo control to prove the point, and it is unlikely that such studies are going to be conducted in the future.

    There is a wealth of grade B and C evidence to support the use of bile acid therapy in this condition and as it is popular with patients its use is likely to continue.

    Cancer surveillance in ulcerative colitis is even more problematical. The evidence cited is all rated grade C, but despite this there is undiminished enthusiasm particularly in the United States for annual colonoscopies in extensive or total ulcerative colitis. This is based on the known higher risk of bowel cancer in ulcerative colitis, particularly in those who also have primary sclerosing cholangitis. However, logically one cannot justify the practice of screening these patients. Indeed one of the best recent pieces of grade A evidence, an 11 year controlled follow up study from Scandinavia, showed that the death rate was actually higher in the screened group because they had more heart attacks and accidents. This may be because of more risky behaviour. There is absolutely no evidence whatsoever that colonoscopic screening in ulcerative colitis saves lives. Overall life expectancy is normal in ulcerative colitis. One wonders whether the main motive for many colonoscopies may not be financial rather than medical.

    The concept of evidence-based medicine is still a question of relative judgments rather than indisputable facts. In the nature of clinical science ideas will change and to remain useful all publications will need very frequent revision and updating.

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