The probability of inevitability: the inherent impossibility of validating criteria for brain death or 'irreversibility' through clinical studies.
A great need persists for diagnostic criteria for both brain death in young children and irreversible loss of consciousness at all ages. This article examines the inferences derived from a hypothetical confirmatory study in which all of the N patients who fulfilled the criterion did in fact experience brain death (irreversibility). A Bayesian methodology proves that, for N in the range of a large clinical study, estimations of prior probabilities are, for all practical purposes, irrelevant to the calculation of the posterior probabilities. The risk of a false positive diagnosis for the next patient who meets the criterion is approximately 1/(N + 2). The chance of at least one false positive diagnosis among the next (N + 1) patients who meet the criterion is around 50 per cent. Thus, achievement of the requisite moral certainty of a declaration of death (irreversibility) necessitates an impossibly large N for the study. This does not mean that one cannot diagnose death, but rather that the validity of the diagnostic criteria must be self-evident on a priori grounds, and that confirmatory studies are necessarily either inadequate or superfluous.
Shewmon
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DA
Department of Pediatrics, UCLA Medical Center 90024.
D000328:Adult; D001499:Bayes Theorem; D001926:Brain Death / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D003128:Coma / Q000175:diagnosis; D003243:Consciousness; D003937:Diagnosis, Differential; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D011237:Predictive Value of Tests; D011336:Probability