How does one make a diagnosis?
Diagnosis is a fascinating area. As anyone who searches Google with a symptom finds (most of us at some time or another), a single symptom can represent anything from the trivial to fatal. This in itself has led to a large increase in consultations, of course.
So how can a doctor synthesise a number of symptoms and come to a view on the likely cause?
It is not something that happens naturally, some clinicians are known, by other clinicians, for their exceptional diagnostic skills. There is always a ‘go to’ clinician in a practice, department or hospital, who others approach with tricky scenarios?
We all though, have to learn from scratch. At medical school we are taught a diagnostic surgical sieve. Starting with a blank canvas we are taught to look at a series of symptoms and see if they fit a category. These would include, genetic, inflammatory, neoplastic, neurological, and several more ending eventually with idiopathic ( that is, nobody knows, there is more of that in medicine than you might assume).
Initially this is long winded and mechanical but it helps us understand the possibilities and to research topics further.
Gradually, with experience we move to pattern recognition, type one thinking, which is almost instantaneous. Sometimes I have narrowed down a likely diagnosis before a patient completes their opening remarks. Type one thinking is open to error though, and this is what we have to guard against. Incidentally, I find that patients often create additional symptoms to fit something they have read on Google. This can lead to errors in our pattern recognition, so please stick to the facts.
Again experience helps us here. After a number of years, one develops a sixth sense, where things do not quite fit the patterns one has seen before. It is then necessary to move to type two thinking. This is the hard thinking that we do before things become automated in our minds. This takes us back to first principals and the surgical sieve, but this time, we can work much more quickly, by understanding which possibilities can safely be excluded, immediately.
We are then left with a small number of possible causes. We can use examination and investigations to further narrow down the possible diagnosis. Though, even then, there may a small possibility of a rare cause of the symptoms which is outside of our learning and experience. A specialist opinion locally or in a tertiary centre in London may then be needed to further elucidate the cause of a symptom.
There is an old saying in medicine though ‘common things are common’ and much of what we see can be given a diagnosis without extensive tertiary investigation.
We still hear, often via third parties about people being ‘misdiagnosed’. Some people certainly are, where, for some reason we are thrown off the correct trail, do not listen carefully enough, or perhaps when symptoms are not typical of a normal presentation. One of the biggest mistakes we make as GPs, is not allowing the patient to express their initial thoughts. We all prepare for a consultation with a planned opening gambit which we hope contains all the salient points. It can also contain vital snippets on our concerns which, if not addressed can leave us disappointed or worried.
More often though, the diagnosis had been considered but another diagnosis was statistically more likely, given available information. As more information becomes available, a diagnosis may change, to reflect this new knowledge.
More on Type 1 and Type 2 thinking can be found in a fascinating book by Daniel Kahneman, Thinking Fast and Slow.
Thank you for reading.
Stay well
Dr Allan Fox
Wye Surgery and www.privategphealthcare.com
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