Background Diagnostic error is commonly defined as a missed, delayed or wrong diagnosis and has been described as among the most important patient safety hazards. Diagnostic errors also account for the largest category of medical malpractice high severity claims and total payouts. Despite a large literature on the incidence of inpatient adverse events, no systematic review has attempted to estimate the prevalence and nature of harmful diagnostic errors in hospitalised patients.

Methods A systematic literature search was conducted using Medline, Embase, Web of Science and the Cochrane library from database inception through 9 July 2019. We included all studies of hospitalised adult patients that used physician review of case series of admissions and reported the frequency of diagnostic adverse events. Two reviewers independently screened studies for inclusion, extracted study characteristics and assessed risk of bias. Harmful diagnostic error rates were pooled using random-effects meta-analysis.

Results Twenty-two studies including 80 026 patients and 760 harmful diagnostic errors from consecutive or randomly selected cohorts were pooled. The pooled rate was 0.7% (95% CI 0.5% to 1.1%). Of the 136 diagnostic errors that were described in detail, a wide range of diseases were missed, the most common being malignancy (n=15, 11%) and pulmonary embolism (n=13, 9.6%). In the USA, these estimates correspond to approximately 249 900 harmful diagnostic errors yearly.

Conclusion Based on physician review, at least 0.7% of adult admissions involve a harmful diagnostic error. A wide range of diseases are missed, including many common diseases. Fourteen diagnoses account for more than half of all diagnostic errors. The finding that a wide range of common diagnoses are missed implies that efforts to improve diagnosis must target the basic processes of diagnosis, including both cognitive and system-related factors.

PROSPERO registration number CRD42018115186.