You are bound to misdiagnose unless you avoid these common mistakes!

5 biases to be aware of when making clinical decisions.

There is evidence to show that our chances of making the wrong diagnosis reduce with our years of experience. I ask the following question: Is there a way to reduce our error rate without waiting for years and years to build experience.

We like to think that we are rational beings but biases affect our decision-making whether we realise it or not, they are mental shortcuts that underpin our gut feelings and choices and can often lead us to systematic errors! By becoming aware of the most common biases, we can learn to recognise them and perhaps make better decisions and avoid errors.

  1. The availability bias

Our brains do not deal well with multiple options, they simplify things to save energy. We have a natural aversion for complexity so we create simple models that we make available to ourselves when solving common or recurrent problems. When it comes to treating hay fever for instance, we will have a small list of antihistamines we tend to always prescribe. The same applies to differential diagnoses. We save energy by creating patterns and we become good at pattern recognition and this affects our choices of treatments and our diagnoses. Of course, guidelines also play a role in supporting this natural mental laziness and this is not always a bad thing; It makes us more efficient as we would burn out had we not had such mechanisms for quick thinking and decision making. Being aware of the availability bias should prompt us to seek other possibilities. Once we make up our mind about a likely diagnosis, It’s worth using a symptom checker or a decision aid tool to make sure we have considered all the options. It takes longer to do that, but in situations where the outcomes could be as serious as cancer, it is best to use an algorithm or a mind map to make sure we crossed the Ts and dotted the Is. Talking to colleagues also help diversify and expand our options.

2. Base rate neglect

When it comes to the availability bias, medical students are probably at the other end of the spectrum as they would probably think of more differential diagnoses. They function more in this respect like a search engine and would be prone to another mental bias: base rate neglect; This is the tendency to ignore the odds of a diagnosis happening. This leads to students coming up with exotic improbable diagnoses. A student would probably consider a brain tumor before a migraine when presented with typical migraine symptoms (and so would a  patient if they google their symptoms most of the time). The more experienced the doctor the less prone they are to base rate neglect.

3. Neglect of probability

When faced with symptoms that could potentially signify cancer but are borderline in meeting the referral criteria, we may feel very uneasy not making a 2WW referral. I am talking about patients below the age limit for a 2WW referral, or who present with findings that could be cancer-related but are below the cutoff values like a mild anaemia or a slight weight loss etc. The probability of such patients having cancer may be significantly lower than those who clearly meet the referral criteria and there usually are other differentials but we find it very hard not to refer them (I certainly do!). In situations like this, we may find ourselves making inappropriate referrals which are more based on fear than on probability. One of the best ways to overcome this bias is discussing the case with colleagues and seeking advice from experts. 

4. Social proofing

Deferring decisions to clinical meetings can have its  downsides. Asking our colleagues for an opinion to back up our provisional diagnosis, is also subject to a bias; Social proofing otherwise described as the herd effect denotes our tendency to follow the group. If a restaurant is full of locals then the food must be good (this is often true!). The risk with clinical meetings is that your colleagues have not actually seen the patient and their decisions and impressions will only be as good as the information you provide. Discussions in clinical meetings are also often limited by time constraints. It is important to bear in mind that even group recommendations can be wrong and we should always re-consider them and put them to the test if new evidence emerges or if we simply have a hunch that they may not be best for our patient.

5. The confirmation bias

This is the tendency to interpret new evidence in the light of what we already believe is true. Overconfidence can be the downfall of an experienced clinician. We may decide that a patient has IBS just from listening to the history but if one element does not fit it is important that we reconsider our judgement. So if the patient mentions weight loss we may systematically want to find an explanation for that weight loss as it is at odds with our initial impression. It is important to recognise this human tendency and therefore ask our questions in a non leading way. So rather than trying to confirm our theories we should be actively seeking to find a fault.

There are dozens of other biases at play in our decision making processes and the more we become aware of them the less prone we will be to errors. It is also important to recognise other factors that can significantly affect our performance. Stress and lack of sleep being the two most prominent ones but I’ll leave these for another post!

I’d love to hear from colleagues regarding this sensitive subject of errors. Have you got specific processes, tools or tricks that you find useful in minimising your risk of error and improving your performance and diagnostic accuracy? If this is the case then please share them by commenting below

Finally, can I take this opportunity to ask my colleagues to consider the work I am doing with my GP colleague Ben Coyle  to promote better training opportunities in general practice by developing a free app called SimplyCPD. Our work is voluntary and free from any pharma funding and partially funded by a grant from the European Regional Development Fund.

If you haven’t yet discovered SimplyCPD - it’s a free CPD-finding app for doctors, designed by doctors and it’s got courses from the big names, all over the UK.  Download it on the app store here or register interest if using Android at - the Android version is practically finished and will be released very soon

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