Weighing the evidence

UNDER THE MICROSCOPE

When I was asked to chair a session at the London School of Economics on evidence-based medicine, I agreed - but with a giggle. Surely, I thought, medicine is based on evidence anyway, and this must be new-fangled nonsense. After listening to Professor David Sackett of Oxford University, though, I have not only become a convert but evangelical.

The most reliable way to assess any medical treatment is by random clinical trials, preferably conducted double blind. In this approach, the treatment is given to some patients and not to others, and so its effectiveness is measured. Patients are assigned to one or other treatment randomly, and neither the patients nor the doctors know who has been given which treatment. If either group is aware of what is going on, this can significantly affect the outcome in subtle ways.

Such trials are a relatively recent procedure in Britain, introduced only in the 1940s. Indeed, trials of any medical treatment were virtually unknown until the pioneering work of Pierre Louis in Paris in the 1830s. Now, however, the procedure is commonplace. Roughly one million randomised clinical trials have been conducted over the last 50 years, and the main problem for doctors is that they simply don't have the time to go searching for such information.

The answer, I now believe, lies in evidence-based medicine - which requires doctors to adopt an evidence-oriented altitude and to become more determined to seek the relevant information. Hitherto this has not been easily available, and traditional review articles have been found to be unreliable: the more self-confident the author, it was concluded, the more unreliable was the article.

Two new sources of information are now available to those who wish to practice this kind of approach. There is a new type of journal, a good example being Evidence-Based Medicine, which screens many other journals and rigorously filters and summarises the key points. The second comes from what is known as the Cochrane Collaboration, an international group that provides systematic reviews by collating the numerous clinical trials.

Not every new treatment needs a fully fledged clinical trial. In some rare cases the results are so dramatic that it would be improper to withhold treatment from those in a trial. An example is the use of a drug based on platinum to treat testicular cancer. While trusting our doctors, perhaps we should all begin to take more responsibility for what treatment they offer us. Many of the treatments provided by our NHS have never been validated by clinical trials, and their effectiveness must remain, for the moment, in doubt. A good beginning might be for all of us to enquire how enthusiastic our doctors are about evidence-based medicine. If you are committed to alternative medicine, though, do not expect an informative response.

! Lewis Wolpert of University College London, is chairman of Copus (the Committee on the Public Understanding of Science).