A healthy state of ignorance

“No one can in five, or even in fifty, years learn all that one could wish about disease and its prevention and treatment. You have to go on learning all your lives, and, a healthy state of ignorance is a saving grace.” So said a Dr Andrews a hundred years ago when welcoming new medical students (p 953). Ignorance is bliss, and economists, practitioners of the dismal science, have a notion of “rational ignorance.” It would be wholly irrational to try to learn everything, yet doctors seem to be prone to the disease of pretending to know more than they do. Nothing could be worse for learning, not least because much of what we “know” is wrong.

Thus it is widely known that you need to request electroencephalography (EEG) in a patient with “funny turns” in order to prove or exclude epilepsy. In fact such an investigation is more likely to mislead than help and may give rise to a wrong diagnosis of epilepsy. A group from Liverpool audited over 400 requests for EEG and decided that over half were inappropriate (p 954). Feedback, education, and guidelines reduced the overall number of requests but still a third were inappropriate. Misconceptions, particularly those inculcated at medical school, go deep: unlearning may be harder than learning.

Iain Chalmers describes how he learnt as a young doctor from Dr Spock's famous book Baby and Childcare that babies should not sleep on their backs—to avoid choking on vomit and flattening their heads (p 998). “We now know,” writes Chalmers, “that the advice . . . led to thousands, if not tens of thousands, of avoidable cot deaths.”

Or consider what gauge needle you should use to perform a lumbar puncture. Most of us were taught, as Susannah Baron describes (p 994), to use a 20 gauge needle, but anaesthetists know (and are supported by evidence from trials) that using a finer gauge, atraumatic needle is simpler, quicker, more effective, and less likely to cause headache. This knowledge unfortunately has not spread far beyond anaesthetists, as Baron has learnt when being given intrathecal injections to treat her non-Hodgkin's lymphoma.

Some things that the world would expect doctors to know they simply don't know. Surely, the world must think, doctors know whether to use antibiotics when treating acute bronchitis. After all, doctors all over the world have been treating tens of millions of cases every year for decades. How could the answer to such a simple question not be known? But it isn't, as an editorial makes clear, despite four systematic reviews (p 939). The problem, the authors suggest, is that the trials have not been clear about which patients have been treated, particularly whether they have any pneumonia. We remain ignorant and in a state of grace.