Wisdom on elusive diagnoses

In the November issue of Canadian Family Physician, Dr Irene Lum brings up the interesting subject of medically unexplained symptoms¹—a burden to doctors and patients alike. This subject underlines a curious paradox: when diagnosis fails medicine, the response is to create another (in this case, “wastebasket”) diagnosis. That is not completely surprising. Diagnosis is medicine’s most important classification tool and the foundation of its practice. So how does medicine account for the things it cannot categorize? It creates a new category.

Early practitioners of scientific medicine seem to have been more patient about cases for which a diagnosis was elusive, and we can draw from their wisdom. Dr H.S. Patterson explained to the medical graduates of Pennsylvania College that “the laws of medicine are too undecided still to be susceptible of a perfect codification.”² Dr Silas Weir Mitchell reminded doctors that they often needed to wait before a disorder provided its “definite shape.”³

Rather than trying to find a diagnosis for everything, medicine might do well to realize that everything might not be diagnosable. Dr D.W. Propst opined in 1939: “It is sometimes impossible to adequately summarize in a name the whole state of a patient’s disequilibrium.”⁴ This view is echoed by Dr Jerome Kassirer in an era closer to our own: “Absolute certainty in diagnosis is unattainable, no matter how much information we gather, how many observations we make, or how many tests we perform … more tests do not necessarily produce more certainty.”⁵

Diagnosis is a very useful medical tool because as it generalizes it also provides a pathway to treatment, explanation, and prognosis; however, it also obfuscates, as it seeks to represent the individual in a generic category that clearly cannot always suit. The old adage “You must treat the patient and not the disease” characterizes medicine’s amazing potential, but at the same time recognizes the limitations of the diagnosis to explain all that ails us. It is probably less important to diagnose those things that medicine cannot explain. Instead, it is more important to ask what medicine can do to help—ofttimes, it can do plenty.

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