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

CONTEXT Misdiagnosis of presumed appendicitis is an adverse outcome that leads to unnecessary surgery. Computed tomography, ultrasonography, and laparoscopy have been suggested for use in patients with equivocal signs of appendicitis to decrease unnecessary surgery. OBJECTIVE To determine if frequency of misdiagnosis preceding appendectomy has decreased with increased availability of computed tomography, ultrasonography, and laparoscopy. DESIGN, SETTING, AND PATIENTS Retrospective, population-based cohort study of data from a Washington State hospital discharge database for 85 790 residents assigned International Classification of Diseases, Ninth Revision procedure codes for appendectomy, and United States Census Bureau data for 1987-1998. MAIN OUTCOME MEASURE Population-based age- and sex-standardized incidence of appendectomy with acute appendicitis (perforated or not) or with a normal appendix. RESULTS Among 63 707 nonincidental appendectomy patients, 84.5% had appendicitis (25.8% with perforation) and 15.5% had no associated diagnosis of appendicitis. After adjusting for age and sex, the population-based incidence of unnecessary appendectomy and of appendicitis with perforation did not change significantly over time. Among women of reproductive age, the population-based incidence of misdiagnosis increased 1% per year (P =.005). The incidence 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 who 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 to unnecessary appendectomy has not changed with the introduction of computed tomography, ultrasonography, and laparoscopy, nor has the frequency of perforation decreased. These data suggest that on a population level, diagnosis of appendicitis has not improved with the availability of advanced diagnostic testing.