Zebra (medical)
Encyclopedia
Zebra is a medical slang
term for a surprising diagnosis
. Although rare diseases are, in general, surprising when they are encountered, other diseases can be surprising in a particular person and time, and so "zebra" is the broader concept.
The term derives from the aphorism
"When you hear hoofbeats behind you, don't expect to see a zebra", which was coined in a slightly modified form in the late 1940s by Dr. Theodore Woodward
, a former professor at the University of Maryland
School of Medicine in Baltimore
. Since horses are the most commonly encountered hoofed animal and zebras are very rare, logically you could confidently guess that the animal making the hoofbeats is probably a horse. By 1960, the aphorism was widely known in medical circles.
As explained by Sotos, medical novices are predisposed to make rare diagnoses because of two synergistic cognitive phenomena: (a) the availability heuristic
("events more easily remembered are judged more probable") combined with (b) the well-known phenomenon, first enunciated in Rhetorica ad Herennium
(circa 85 BC), that "the striking and the novel stay longer in the mind." Thus, the aphorism has a valid role in teaching medical students to be better diagnosticians.
Three master diagnosticians have noted, however, that cautions against making surprising diagnoses (e.g. of a rare disease) are not valid in practitioners with greater knowledge and experience:
A related, but distinct, term for an obscure and rare diagnosis in medicine is fascinoma.
Medical slang
Medical slang is a form of slang used by doctors, nurses, paramedics and other hospital or medical staff. Its central aspect is the use of facetious but impressive-sounding acronyms and invented terminology to describe patients, co-workers or tricky situations. It serves, in other words, as a...
term for a surprising diagnosis
Diagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
. Although rare diseases are, in general, surprising when they are encountered, other diseases can be surprising in a particular person and time, and so "zebra" is the broader concept.
The term derives from the aphorism
Aphorism
An aphorism is an original thought, spoken or written in a laconic and memorable form.The term was first used in the Aphorisms of Hippocrates...
"When you hear hoofbeats behind you, don't expect to see a zebra", which was coined in a slightly modified form in the late 1940s by Dr. Theodore Woodward
Theodore Woodward
Theodore E. Woodward was an American medical researcher in the field of medicine at the University of Maryland, Baltimore. In 1948, he received a Nobel Prize nomination for his role in finding cures for typhus and typhoid fever.-Biography:Born in Westminster, Maryland the son of Lewis K. Woodward,...
, a former professor at the University of Maryland
University of Maryland, Baltimore
University of Maryland, Baltimore, was founded in 1807. It comprises some of the oldest professional schools in the nation and world. It is the original campus of the University System of Maryland. Located on 60 acres in downtown Baltimore, Maryland, it is part of the University System of Maryland...
School of Medicine in Baltimore
Baltimore
Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...
. Since horses are the most commonly encountered hoofed animal and zebras are very rare, logically you could confidently guess that the animal making the hoofbeats is probably a horse. By 1960, the aphorism was widely known in medical circles.
As explained by Sotos, medical novices are predisposed to make rare diagnoses because of two synergistic cognitive phenomena: (a) the availability heuristic
Availability heuristic
The availability heuristic is a phenomenon in which people predict the frequency of an event, or a proportion within a population, based on how easily an example can be brought to mind....
("events more easily remembered are judged more probable") combined with (b) the well-known phenomenon, first enunciated in Rhetorica ad Herennium
Rhetorica ad Herennium
The Rhetorica ad Herennium, formerly attributed to Cicero but of unknown authorship, is the oldest surviving Latin book on rhetoric, dating from the 90s BC, and is still used today as a textbook on the structure and uses of rhetoric and persuasion....
(circa 85 BC), that "the striking and the novel stay longer in the mind." Thus, the aphorism has a valid role in teaching medical students to be better diagnosticians.
Three master diagnosticians have noted, however, that cautions against making surprising diagnoses (e.g. of a rare disease) are not valid in practitioners with greater knowledge and experience:
A related, but distinct, term for an obscure and rare diagnosis in medicine is fascinoma.
Other medical aphorisms
- Sutton's lawSutton's lawSutton's law states that when diagnosing, one should first consider the obvious. It suggests that one should first conduct those tests which could confirm the most likely diagnosis...
- perform first the diagnostic test expected to be most useful - Occam's razorOccam's razorOccam's razor, also known as Ockham's razor, and sometimes expressed in Latin as lex parsimoniae , is a principle that generally recommends from among competing hypotheses selecting the one that makes the fewest new assumptions.-Overview:The principle is often summarized as "simpler explanations...
- select from among competing hypotheses the one that makes the fewest new assumptions - Leonard's Law of Physical Findings - it's obvious or it's not there
- KISS principleKISS principleKISS is an acronym for the design principle Keep it simple, Stupid!. Other variations include "keep it simple and stupid", "keep it short and simple", "keep it simple sir", "keep it simple or be stupid" or "keep it simple and straightforward"...
- Keep It Simple, Stupid - Hickam's dictumHickam's dictumHickam's dictum is a counterargument to the use of Occam's razor in the medical profession. The principle is commonly stated: "Patients can have as many diseases as they damn well please". The principle is attributed to John Hickam, MD...
- "Patients can have as many diseases as they damn well please"