A recent study on heart attack prevention strategies reached the opposite of the expected conclusion. Dalrymple comments on the danger of assumptions in medical testing at Pajamas Media:
There are few phrases more dangerous in medicine than “It stands to reason,” because what stands to reason may in fact not be a good idea, however brilliant it may once have seemed. This is because reality is always more complex than our theories about it; grey is theory, said Goethe, but green i[s] the tree of life.
Perhaps the greatest single intellectual advance in the medicine of the last century was the realization that “it stands to reason” is no reason at all; everything must be studied in the light of experience. There was a good example of this necessity in a recent edition of the New England Journal of Medicine, which studied the effect of giving patients doses of aspirin or clonidine before and after undergoing non-cardiac surgery.
I am a medical statistic. I had a deep-vein thrombosis and was removed from an aircraft at Heathrow by ambulance. Therefore, I am now amongst the ranks of the ‘deep-vein thrombosis following long-haul flight’ brigade. Except that I am not. Mine occurred 48 hours before boarding the plane, but I did not recognise it for what it was. Of course, the “stands to reason” rule applied, and nothing I could say to the doctors at the hospital or my GP would change their minds.