Patients who are perceived by their medical practitioners as being "difficult" are more likely to be misdiagnosed, a study has found.

Patients who are deemed to be "difficult" are more likely to receive a misdiagnosis from their doctor, new research suggests.

Medics who are dealing with problematic behaviour are less likely to digest and process clinical information properly, the studies conclude.

Difficult patients are also deemed to be less "likeable" than ones who have act in a neutral way, the authors found.

The research papers, published in BMJ Quality and Safety, tested physicians diagnostic skills when presented with different case scenarios including detail on the patients' behaviours.

In the first study, 63 doctors in their final year of training in family medicine were presented with one of two versions of six clinical case scenarios - one version portrayed a "difficult" patient while the other depicted a "neutral" one.

The "difficult" behaviours illustrated by the patients in the scenarios included: aggression, a patient questioning a doctor's competence, one who ignores the doctor's advice, a patient who has low expectations of their doctor's support and another who presents as "utterly helpless".

The medics were also asked to diagnose both complex and simple cases.

They were then asked to write down the most likely diagnosis as quickly as possible and then to review the same case. They were also asked about the likeability of the patient.

Doctors were 42 per cent more likely to misdiagnose a difficult patient than a neutral one in a complex case, and six per cent more likely to do so in a simple case, the researchers found.

The average likeability ratings were also significantly lower for patients portrayed as difficult than they were for those portrayed as behaving neutrally.

The authors conclude: "Difficult patients can indeed adversely affect doctors' diagnostic reasoning.

"While diagnosing clinical cases that were exactly the same, except for the description of the patient's behaviours, participants provided less accurate diagnoses when the patient presented with disruptive behaviours than with neutral behaviours."

In a second paper, 74 trainee hospital doctors were asked to diagnose eight clinical case scenarios, half of which involved difficult behaviours and half of which involved neutral behaviours.

Diagnostic accuracy was 20 per cent lower for difficult patients, the Dutch researchers found.

"Difficult patients' behaviours induce doctors to make diagnostic errors, apparently because doctors spend part of their mental resources on dealing with the difficult patients' behaviours, impeding adequate processing of clinical findings," the authors concluded.

In a linked editorial, Dr Donald Redelmeier and Dr Edward Etchells of the Centre for Quality Improvement and Patient Safety, University of Toronto, Canada, wrote: "These results agree with many past analyses indicating that unpleasant people tend to have unfavourable outcomes."

They add: "Physicians need safeguards against the negative emotions that may undermine diagnostic accuracy."

They suggest that to avoid misdiagnoses of difficult patients, doctors should perform more self reflection after patient encounters, more teamwork and consultation and consider checklists or computer assisted diagnostics.