Kieran Walsh: Finding your way back from the wrong diagnosis

A 40 year old man has a cough—but his GP cannot find out the cause. Eventually the patient is referred to the local hospital where he is diagnosed with asthma. The doctor who sees him starts inhalers. But the inhalers don’t work and so he goes back for another appointment. The next doctor that he sees increases the dose of the inhalers. But this doesn’t work either so eventually the patient starts on oral steroids. These don’t help either. Finally the patient has some further tests and is diagnosed with gastro-esophageal reflux. He receives treatment for this, stops his inhalers, and gets better.

This is a fictional scenario, but stories like this happen all the time in real life. We can look at the story from a number of perspectives—but one way of looking at it is from the perspective of cognitive bias. In this case the cognitive bias is likely one of anchoring or diagnosis momentum. Once a patient receives a diagnostic label, it is difficult to remove and replace it. In this scenario the doctor thought the patient had asthma and more doctors continued down this diagnostic and treatment pathway until they ran out of road. They eventually got to the correct diagnosis but clearly could have got there faster. This story ended fairly happily with a delayed diagnosis of a benign and treatable condition. But the patient could just as easily have had lung cancer and then the lesson learned would have had a bitter aftertaste.

So what can we do to stop this happening? Maybe if we educate doctors about cognitive biases, then they would be more likely to recognise their own cognitive biases and less likely to make mistakes. Right? Wrong. The evidence shows that education to reduce cognitive biases has little or no effect on diagnostic errors. This paper by Norman et al has just been published and so opens up thinking in this area for the rest of 2017. So if education to stop cognitive biases won’t help, what will? This is a complex problem and the answer to it is complex, nuanced and dependent on circumstances.

Let’s look at the story again—this time from the perspective of knowledge based strategies. Let’s say that the doctor stopped when the patient didn’t respond to the inhalers. Let’s say that they stopped and analysed the information that they had and thought about what else the diagnosis could be and maybe identified new knowledge that would help them. And then they thought about the differential diagnosis of asthma and came up with the correct diagnosis. The evidence shows that this strategy is more likely to work. So knowledge deficits are important.

How we help with knowledge is a whole different story. Healthcare professionals need knowledge that is current, reliable, and evidence based and at the same time will help them quickly answer the specific clinical question that they have. But too often they don’t get this type of knowledge. Rather they get too much knowledge that is unwieldy, that answers other people’s questions rather than those of their patients and that is sometimes not evidence based.

However the area is even more complex than this—there are a range of nuances and caveats. Healthcare professionals are short of time and sometimes don’t have time to stop and think and look things up. This must be addressed. But in the meantime knowledge must be available at the point of care and in a format that healthcare professionals can use. This in turn depends on circumstances—but is likely to mean on a mobile or app or whatever device is being used.

The literature is currently pointing back to knowledge as a vital resource that can reduce error and improve the quality of care. Providers of knowledge can help by changing how they deliver knowledge and ensuring that they work to high standards and, as importantly, to the right standards. In this regard, currency, evidence base and applicability are all important.

Kieran Walsh is clinical director of BMJ Learning—the education service of the BMJ Group. He is responsible for the editorial direction of BMJ Online Learning, BMJ Masterclasses, and BMJ onExamination. He has written two books—the first on cost and value in medical education and the second a dictionary of medical education quotations. He has worked in the past as a hospital doctor – specialising in care of the elderly medicine and neurology.


  1. NormanGR, Monteiro SD, Sherbino J, Ilgen JS, Schmidt HG, Mamede S. The Causes of Errors in Clinical Reasoning: Cognitive Biases, Knowledge Deficits, and Dual Process Thinking. Acad Med.2017 Jan;92(1):23-30.

Competing interests: KW works for BMJ, which produces BMJ Best Practice – an evidence-based clinical decision support tool.