46:: "When you hear hoofbeats behind you, don't expect to see a zebra." (Since zebras are much rarer than horses in the United States, the sound of hoofbeats would almost certainly be from a horse.) By 1960, the aphorism was widely known in medical circles. The saying is a warning against the statistical
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In making the diagnosis of the cause of illness in an individual case, calculations of probability have no meaning. The pertinent question is whether the disease is present or not. Whether it is rare or common does not change the odds in a single
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is considered a rare condition and those with it are known as medical zebras. The zebra was adopted across the world as the EDS mascot to bring the patient community together and raise awareness.
70:), "the striking and the novel stay longer in the mind." Thus, the aphorism is an important caution against these biases when teaching medical students to weigh medical evidence.
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page 1. Woodward's original version was: "Don't look for zebras on Greene Street", the street on which the
University of Maryland medical campus is sited.
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Diagnosticians have noted, however, that "zebra"-type diagnoses must nonetheless be held in mind until the evidence conclusively rules them out:
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Dundes, Lauren, Michael B. Streiff, and Alan Dundes. "When You Hear
Hoofbeats, Think Horses, Not Zebras": A Folk Medical Diagnostic Proverb."
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species are rare or not present. This is a matter of concern because such misdiagnoses can delay correct diagnosis and treatment.
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If the diagnosis can be made on the basis of specific criteria, then these criteria are either fulfilled or not fulfilled.
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where the likelihood of something like a disease among the population is not taken into consideration for an individual.
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314:(Araneae, Sicariidae): a review of biological, medical and psychological aspects regarding envenomations"
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Medical novices are predisposed to make rare diagnoses because of (a) the
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Leonard's law of physical findings – it is obvious or it is not there
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Exotic diagnosis in medicine which is usually unnecessary and wrong
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Comparable slang for an obscure and rare diagnosis in medicine is
159:– "Patients can have as many diseases as they damn well please"
144:– perform first the diagnostic test expected to be most useful
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skin lesions in the United States are often diagnosed as
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A. McGehee Harvey, James
Bordley II, Jeremiah Barondess
212:– Extraordinary claims require extraordinary evidence
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190:Medical axioms, aphorisms, and clinical memoranda
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357:"Why the zebra? – The Ehlers-Danlos Support UK"
429:. Mt. Vernon, VA: Mt. Vernon Book Systems.
200:Commentary on the aphorisms of Hippocrates
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40:University of Maryland School of Medicine
427:Zebra Cards: An Aid to Obscure Diagnoses
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172:– awareness ribbon for rare diseases
393:Harvey, A. M.; et al. (1979).
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395:Differential Diagnosis (3rd ed.)
26:for a surprising, often exotic,
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136:Other medical aphorisms
475:Philosophy of medicine
322:Journal of Arachnology
310:"Spiders of the genus
130:Ehlers–Danlos syndrome
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60:Rhetorica ad Herennium
55:availability heuristic
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42:, who instructed his
465:Razors (philosophy)
455:Medical terminology
38:, professor at the
335:10.1636/rst08-06.1
274:16 (1999): 95–104.
170:Zebra print ribbon
436:978-0-9818193-0-3
406:Medical Detective
48:base rate fallacy
36:Theodore Woodward
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68: 85 BC
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362:October 28,
329:: 150–163.
111:loxoscelism
449:Categories
312:Loxosceles
272:Proverbium
223:References
196:Maimonides
176:Samuel Gee
119:Loxosceles
95:fascinoma
379:page 15.
298:page 15.
164:See also
107:Necrotic
102:Examples
85:—
78:patient.
32:aphorism
343:7746032
286:page 7.
237:page 1.
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192:(1924)
182:(1902)
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339:S2CID
317:(PDF)
125:Usage
20:Zebra
431:ISBN
412:ISBN
364:2021
202:and
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