Working out whether a treatment works, and for how many people, is trickier than it sounds. Here’s how you should go about doing it
WHEN I had been a doctor for ten years, I enrolled in a postgraduate course in epidemiology and biostatistics. It was at a time when my brain could still absorb information like a damp Wettex, and I found the subject matter engrossing.
The course was based on the work of a doctor at Canada’s McMaster University, David Sackett, who had created the discipline known as clinical epidemiology in the 1970s. Sackett subsequently moved to Oxford University and renamed his creation evidence-based medicine, or EBM. Although he had been trained in epidemiology, back in clinical practice he was disturbed to find that so much medical decision-making was unstructured and not based on a proper analysis of research findings.
Like all champions of new movements, some of the proponents of EBM had a zealous air about them. It was not surprising that their born-again enthusiasm would annoy the proletariat of “humble” practising clinicians, but some parts of the academic medical world were also miffed. Many thought EBM was a tautology. How could the practice of medicine be anything but based on evidence? The Lancet published a snooty editorial in 1995 that grudgingly acknowledged the emergence of the movement. It was titled “Evidence-Based Medicine – In Its Place.”
During my studies I discovered that EBM held answers to many of the problems I had identified in my work. I began to see that I didn’t really know how to judge if the drugs I was prescribing were effective or how to interpret the tests I ordered. Previously I had relied on the wisdom of my elders, but now I saw that there was a relatively simple way to turn my half-baked medical intuitions into something more concrete and scientific. EBM was about turning qualitative notions into semi-quantitative conclusions, I learnt, so you had to be prepared to work with a few simple formulae.
One of these would allow me to calculate a number that I believe should be known to every doctor and every patient. Indeed, it would become my favourite number…
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