I was talking to a composer a few weeks ago. “This stuff doesn’t really exist except when it’s played,” he said, pointing to his score with heavy despair. “Whereas you’ve got a job where you can actually see that you are doing something good.” He couldn’t understand that my protests to the contrary were genuine: doctors cannot always be sure that they are making a positive difference.

Medical history is stuffed with examples of bad practice – lobotomy for just about anyone with a mental health problem, tonsillectomy for most people with a sore throat, bed rest for everyone with low back pain. I may exaggerate, but only a little. Even now, we don’t seem to appreciate the value of analysing what we are doing.

The US Senate has just passed a bill putting $1.1bn into research aimed at identifying which medical treatments work and which don’t. This sounds like a good idea, but of course not all research is created equal. Regular readers will be aware, for example, of the conflicts surrounding the Department of Health recommendation that all over-65s receive a flu vaccination. Some evidence supports vaccination, some indicates that it does not improve mortality rates. What to believe?

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