Intended for healthcare professionals


Errors in clinical reasoning: causes and remedial strategies

BMJ 2009; 338 doi: (Published 08 June 2009) Cite this as: BMJ 2009;338:b1860
  1. Ian A Scott, associate professor of medicine
  1. 1Department of Internal Medicine and Clinical Epidemiology, Princess Alexandra Hospital, Ipswich Road, Brisbane, Australia 4102
  1. Correspondence to: I A Scott ian_scott{at}
  • Accepted 4 January 2009

Everyone makes mistakes, but greater awareness of the causes would help clinicians to avoid many of them, as Ian Scott explains

Most errors in clinical reasoning are not due to incompetence or inadequate knowledge but to frailty of human thinking under conditions of complexity, uncertainty, and pressure of time. To minimise such cognitive error we need to understand its prevalence and causes. In this article I discuss why errors occur and describe strategies that may help avoid them.

Prevalence of reasoning error

The first step to optimal care is making the correct diagnosis, which is missed or delayed in between 5% and 14% of acute hospital admissions.1 2 Autopsy studies confirm diagnostic error rates of 10-20%,3 4 with autopsy disclosing previously undiagnosed problems in up to 25% of cases.3 Even if the diagnosis is correct, up to 45% of patients with acute or chronic medical conditions do not receive recommended evidence based care,5 while between 20% and 30% of administered investigations and drugs are potentially unnecessary.6 Clinicians are sometimes less willing to adopt new beneficial interventions than to abandon old ineffective ones.7

The extent to which these deficits relate directly to reasoning error by clinicians, rather than environmental determinants beyond their control, remains uncertain, although recent studies of adverse events in hospital patients may give some indication.8 9 A third of the identified adverse events involved errors of execution (slips, lapses, or oversights in carrying out appropriate management in correctly diagnosed patients), but almost half involved errors of reasoning or decision quality (failure to elicit, synthesise, decide, or act on clinical information). Such reasoning errors led to death or permanent disability in at least 25% of cases, and at least three quarters were deemed highly preventable.9

Of some concern is the discrepancy between prevalence of reasoning …

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