Has misdiagnosis of appendicitis decreased over time? A population-based analysis

Context Misdiagnosis of presumed appendicitis is an adverse outcome that le ads to unnecessary surgery. Computed tomography, ultrasonography, and lapar oscopy have been suggested for use in patients with equivocal signs of appe ndicitis to decrease unnecessary surgery. Objective To determine if frequency of misdiagnosis preceding appendectomy has decreased with increased availability of computed tomography, ultrasono graphy, and laparoscopy. Design, Setting, and Patients Retrospective, population-based cohort study of data from a Washington State hospital discharge database for 85790 resid ents assigned International Classification of Diseases, Ninth Revision proc edure codes for appendectomy, and United States Census Bureau data for 1987 -1998. Main Outcome Measure Population-based age- and sex-standardized incidence o f appendectomy with acute appendicitis (perforated or not) or with a normal appendix. Results Among 63707 nonincidental appendectomy patients, 84.5% had appendic itis (25.8% with perforation) and 15.5% had no associated diagnosis of appe ndicitis. After adjusting for age and sex, the population-based incidence o f unnecessary appendectomy and of appendicitis with perforation did not cha nge significantly over time. Among women of reproductive age, the populatio n-based incidence of misdiagnosis increased 1% per year (P =.005). The inci dence of misdiagnosis increased 8% yearly in patients older than 65 years ( P<.001) but did not change significantly in children younger than 5 years ( P =.17). The proportion of patients undergoing laparoscopic appendectomy wh o were misdiagnosed was significantly higher than that of open appendectomy patients (19.6% vs 15.5%; P<.001). Conclusion Contrary to expectation, the frequency of misdiagnosis leading t o unnecessary appendectomy has not changed with the introduction of compute d tomography, ultrasonography, and laparoscopy, nor has the frequency of pe rforation decreased. These data suggest that on a population level, diagnos is of appendicitis has not improved with the availability of advanced diagn ostic testing.