BOX 7.12 The Cochrane Collaboration

Health care professionals, consumers, researchers, and policy makers are overwhelmed with unmanageable amounts of information. In an influential book published in 1972, Archie Cochrane, a British epidemiologist, drew attention to our great collective ignorance about the effects of health care. He recognized that people who want to make more informed decisions about health care do not have ready access to reliable reviews of the available evidence.

In 1987, the year before Cochrane died, he referred to a systematic review of randomized controlled trials (RCTs) of care during pregnancy and childbirth as "a real milestone in the history of randomized trials and in the evaluation of care," and suggested that other specialties should copy the methods used. In the same year, the scientific quality of many published reviews was shown to leave much to be desired. As Cochrane had emphasized, reviews of research evidence must be prepared systematically and they must be kept up-to-date to take account of new evidence.

If this is not done, important effects of health care (good and bad) will not be identified promptly, and people using the health services will be ill-served as a result. In addition, without systematic, up-to-date reviews of previous research, plans for new research will not be well informed. As a result, researchers and funding bodies will miss promising-leads and will embark on studies asking questions that have already been answered.

The Cochrane Collaboration Logo

The Cochrane Collaboration logo illustrates a systematic review of data from seven randomized controlled trials, comparing one health care treatment with a placebo. Each horizontal line represents the results of one trial (the shorter the line, the more certain is the result); the diamond represents their combined results. The vertical line indicates the position around which the horizontal lines would cluster if the two treatments compared in the trials had similar effects; if a horizontal line touches the vertical line, it means that that particular trial found no clear difference between the treatments. The position of the diamond to the left of the vertical line indicates that the treatment studied is beneficial. Horizontal lines or a diamond to the right of the line would show that the treatment did more harm than good.

This diagram shows the results of a systematic review of RCTs of a short, inexpensive course of a corticosteroid given to women about to give birth prematurely. The first RCT was reported in 1972. The diagram summarizes the evidence that would have been revealed had the available RCTs been reviewed systematically a decade later: it indicates strongly that corticosteroids reduce the risk of babies' dying from the complications of immaturity. By 1991, seven more trials had been reported, and the picture had become still stronger. This treatment reduces by 30 to 50 percent the odds that the babies of these women will die from the complications of immaturity.

Because no systematic reviews of these trials were published until 1989, most obstetricians did not realize that the treatment was so effective. As a result, tens of thousands of premature babies probably suffered and died unnecessarily (and received more expensive treatment than was necessary). This is just one of many examples of the human costs resulting from failure to perform systematic, up-to-date reviews of RCTs of health care.

SOURCE: The Cochrane Collaboration, 1999.



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