The Razor, the Zebra and the Need to Know

By Rick Rader, MD

In regard to assigning the value of a correct diagnosis, it was Mahatma Gandhi, not a clinician, who offered, “A correct diagnosis is three-fourths the remedy.”  He might have underestimated it.

This month’s cover of HELEN spotlights the “Undiagnosed” community, and we are delighted to promote the Wilhelm Foundation and the ongoing global work of medical detectives.

One of my medical heroes, Sir William Osler, the Doyen of American medical education and one of the founders of the Johns Hopkins Medical School, often reminded his medical students, “Listen to your patient, he is telling you the diagnosis.”  While this Oslerian pearl is invaluable, it is unfortunately not the infallible rule.

There is an old medical adage that suggests, “there are 10,000 diseases and just 500 cures.”  The problem is to ascertain (with a high degree of certainty) which belongs to which patient. One of the tools available to the astute clinician is the “differential diagnosis.”  This refers to a list of possible conditions that may be causing a person’s symptoms. A doctor will base this list on several factors, including a person’s medical history and the results of any physical examinations and diagnostic tests.  As the physician begins to whittle down the list, the hope is that what remains is the root of the pathology.  One of the tools in the clinician’s white coats is Occam’s Razor. It’s not a real razor, but a philosophical razor that suggests that the simplest solution is typically the correct one. Oh, if only that was always a reliable axiom.  The fallacy is that the simplest solution is not always the correct one.

Another pearl that is hurled around grand rounds is the reference to the “so-called zebra.”  Attributed to Dr. Theodore Woodward the phrase, “When you hear hoofbeats behind you, don’t expect to see a zebra,” serves as another reminder to not complicate or muddy the road to a diagnosis.  Again the “zebra” and the “razor” are not always reliable, accurate and appropriate clues and roads to a correct diagnosis.

One thing is certain, and that despite the inability to announce a definitive diagnosis, the ongoing need to support, treat, and comfort the patient is provided with compassion and empathy.

HELEN salutes the efforts of the Undiagnosed Disease Community in their pursuit of unlocking the mysteries of diagnostic uncertainty. We are particularly indebted to the patients, families and advocates who have committed to expanding the horizons of these diagnostic dilemmas.