Differential diagnosis needs documenting in primary care shows paper

A landmark article published yesterday in “JAMA Internal Medicine” entitled “Types and Origins of Diagnostic Errors in Primary Care Settings” once again highlights the importance and value of traditional clinical skills and the differential diagnosis.

The study looked at 190 cases of diagnostic error highlighted by triggers within the medical record such as unexpected return visits etc. rather than malpractice suits. The settings were two large sites each with a list size of around 50,000 patients-one was public health (Veterans Administration) and the other an integrated private healthcare system. The key points from the paper for us were:

• This study identified cases of diagnostic error by looking at triggers such as unexpected return visits, unplanned hospitalisations or Emergency Department visits a short time after the initial primary care visit rather than analyses of malpractice claims that often over represent cancers and other claims where the legal basis for the claim is strong with a good paper trail.
• In both sites the mean average age of the patient who experienced a diagnostic error was older. In one it was 66.5 versus 62.7 and at the other it was 53.8 versus 45.6. No surprise with older patients having more complex presentations.
• 68 unique diagnoses were missed in the 190 cases. Most of the diagnoses were common with renal failure at the top (5.8%). Unlike the results from the analysis of malpractice claims, the spread of diagnoses is much wider and not nearly so focussed on cancer which only accounted for 5.8% of the cases. As the authors comment, this demonstrates why single disease strategies have little impact on the overall picture. Any strategy to improve diagnosis in primary care will need to be broadly based. It also shows that, to the old medical adage ‘common things occur commonly’, should also be added ‘and also commonly get missed’.
• The presenting symptoms for the cases were highly variable and in 1/3 of the cases did not appear to bear a direct relationship to the condition that was missed. This shows that delays in diagnosis are not just about the rare and esoteric but far more often about non-classic presentations of common diseases.
• Another notable finding reported by the authors was the absence of documentation of the differential diagnosis –“a fundamental step in the diagnostic reasoning process”. They continue to state how their findings highlight the need to focus on the basic clinical skills and related clinical reasoning skills rather than a reliance on technology such as lab tests and imaging.
• The authors added that patient empowerment and engagement in the diagnostic process would also greatly add to a diagnosis improvement strategy.

Overall, this is a very revealing paper by Hardeep Singh (one of the most experienced researchers in the area of diagnostic error) and his colleagues. The points raised argue strongly for the requirement that the differential diagnosis should be documented and the patient encouraged to be a partner in this process. The Isabel tools help greatly in both these areas.

The invited commentary to the paper by David Newman Toker is interesting as his estimate of the number of people who might have experienced misdiagnosis related harm has now been put at 150,000 annually in the US alone!

In looking at solutions the commentary states “The answers may well lie in hybrid solutions such as “generically” training physicians in the most effective use of computer based diagnostic decision support tools…”

The role of primary care physicians has expanded, and will continue to do so, with respect to the variety and complexity of medical conditions, which must be evaluated during relatively brief patient encounters. In the light of this, primary physicians should arm themselves with diagnostic decision support aids, like Isabel, and also encourage their patients to help them as much as possible in the diagnostic process; a problem shared is a problem halved.