Maintaining an open mind – being willing to revise an initial diagnosis
This is an aspect that cannot be overstated. MPS case files stand testimony to the many instances in which a patient’s failure to respond to treatment is plainly indicating that it is time to review the diagnosis, yet the patient’s doctors blindly persist with it (the case report, "Turning a deaf ear" is a good example). This is a cognitive weakness that all clinicians should be aware of and guard against.
Experts in human factors call the phenomenon “diagnostic fixation”, and have described it in the following terms:
“When examined in retrospect, the factors that led to a missed or significantly delayed medical diagnosis often seem starkly conspicuous:
- a quick, confident diagnosis was made
- contrary evidence that kept presenting was ignored.”7
Case report: Turning a deaf ear
The history was recorded as persistent, offensive discharge from the right ear as well as continuing pain
E was a 12-year-old girl who had been complaining of earache for a week after coming back from an activity holiday. Despite taking paracetamol suspension, the pain persisted and her mother, Mrs K, brought her along to be reviewed by her regular GP, Dr T. E was well known to Dr T as he had seen her on a number of occasions with mild asthma. Dr T documented the history of pain in her right ear. She was noted to be apyrexial and systemically well, with a normal appetite.
The only abnormal examination finding was debris and inflammation in the right external auditory meatus. E was diagnosed with otitis externa and prescribed topical antibiotic drops, as well as regular paracetamol suspension. Mrs K was given advice about helping E to avoid getting water in her ear, and to avoid swimming until the symptoms had cleared up.
Despite the drops the earache continued and Mrs K brought E to the practice again four days later to see another GP, Dr A. The history was recorded as persistent, offensive discharge from the right ear as well as continuing pain. A swab was taken and sent for culture. A course of oral antibiotics was prescribed for what was felt to be persistent otitis externa.
Unfortunately, despite both topical and oral antibiotics E’s symptoms continued over the ensuing weeks. During this time E was brought in by her parents on multiple occasions and she was reviewed by a number of different GPs at the practice. Mr and Mrs K became increasingly concerned regarding their daughter’s ongoing symptoms.
Six weeks after E had seen Dr T for the first time, he reviewed her again. Dr T checked the swab result, which had shown a growth of pseudomonas. It was noted that the pseudomonas was sensitive to the antibiotics that had been given to E at the last consultation. On this occasion Dr T documented that the ear discharge had persisted for several weeks and noted it to be blood-stained on otoscopy. Dr T then prescribed both antibiotic ear spray and drops.
Finally, eight weeks after the first presentation, E saw Dr S who referred her to an ENT consultant. Detailed otoscopy suggested an abnormality in the appearance of the tympanic membrane, and an urgent CT was requested. Sadly this revealed a cholesteatoma and surgical treatment was necessary.
E was brought in by her parents on multiple occasions and she was reviewed by a number of different GPs at the practice
E was left with permanent hearing loss in her right ear. A claim was started against several of the doctors involved in this case.
On reviewing the notes it was found that none of the doctors had documented whether or not the tympanic membrane was visible, and no-one had commented on any associated hearing loss. GP experts were highly critical of the care provided by the GPs involved.
It was felt that such a long history of discharge (especially blood-stained) should have raised suspicions of a cholesteatoma. Prompt specialist opinion should have been sought when the symptoms failed to resolve. The case was settled for a moderate sum.
None of the doctors had documented whether or not the tympanic membrane was visible, and no-one had commented on any associated hearing loss
The “quick, confident diagnosis” is usually made by employing heuristics (in other words, a “rule of thumb”). Heuristics, while useful, may easily lead one astray because they depend on a range of cognitive biases, a few of which are described in Box 13. So, if you diagnose using heuristics (which almost all doctors do), it is imperative that you do not fixate on your initial diagnosis and remain open to new information that may contradict it.
Box 13: Heuristics-based diagnosis
Shortcuts in reasoning occur on a subconscious level, employing a variety of heuristics. Some of those commonly used in diagnosis are:
- Availability heuristic – likelihood is judged by how easily examples spring to mind.
- Anchoring heuristic – the tendency to stick with initial impressions.
- Premature closure – failure to pursue several alternatives.
- Framing effects – different decisions made depending on how information is presented.
Redelmeier D, The Cognitive Psychology of Missed Diagnosis, Annals of Internal Medicine (2005)