Factors Associated With Potentially Missed Diagnosis of Appendicitis in the Emergency Department.

Importance: Appendicitis may be missed during initial emergency department (ED) presentation. Objective: To compare patients with a potentially missed diagnosis of appendicitis (ie, patients with symptoms associated with appendicitis, including abdominal pain, constipation, nausea and/or vomiting, fever, and diarrhea diagnosed within 1-30 days after initial ED presentation) with patients diagnosed with appendicitis on the same day of ED presentation to identify factors associated with potentially missed appendicitis. Design, Setting, and Participants: In this cohort study, a retrospective analysis of commercially insured claims data was conducted from January 1 to December 15, 2019. Patients who presented to the ED with undifferentiated symptoms associated with appendicitis between January 1, 2010, and December 31, 2017, were identified using the Clinformatics Data Mart administrative database (Optum Insights). The study sample comprised eligible adults (aged ≥18 years) and children (aged <18 years) who had previous ED visits within 30 days of an appendicitis diagnosis. Main Outcomes and Measures: Potentially missed diagnosis of appendicitis. Adjusted odds ratios (AORs) for abdominal pain and its combinations with other symptoms associated with appendicitis were compared between patients with a same-day diagnosis of appendicitis and patients with a potentially missed diagnosis of appendicitis. Results: Of 187 461 patients with a diagnosis of appendicitis, a total of 123 711 (66%; 101 375 adults [81.9%] and 22 336 children [18.1%]) were eligible for analysis. Among adults, 51 923 (51.2%) were women, with a mean (SD) age of 44.3 (18.2) years; among children, 9631 (43.1%) were girls, with a mean (SD) age of 12.2 (18.2) years. The frequency of potentially missed appendicitis was 6060 of 101 375 adults (6.0%) and 973 of 22 336 children (4.4%). Patients with isolated abdominal pain (adults, AOR, 0.65; 95% CI, 0.62-0.69; P < .001; children, AOR, 0.79; 95% CI, 0.69-0.90; P < .001) or with abdominal pain and nausea and/or vomiting (adults, AOR, 0.90; 95% CI, 0.84-0.97; P = .003; children, AOR, 0.84; 95% CI, 0.71-0.98; P = .03) were less likely to have missed appendicitis. Patients with abdominal pain and constipation (adults, AOR, 1.51; 95% CI, 1.31-1.75; P < .001; children, AOR, 2.43; 95% CI, 1.86-3.17; P < .001) were more likely to have missed appendicitis. Stratified by the presence of undifferentiated symptoms, women (abdominal pain, AOR, 1.68; 95% CI, 1.58-1.78; nausea and/or vomiting, AOR, 1.68; 95% CI, 1.52-1.85; fever, AOR, 1.32; 95% CI, 1.10-1.59; diarrhea, AOR, 1.19; 95% CI, 1.01-1.40; and constipation, AOR, 1.50; 95% CI, 1.24-1.82) and girls (abdominal pain, AOR, 1.64; 95% CI, 1.43-1.88; nausea and/or vomiting, AOR, 1.74; 95% CI, 1.42-2.13; fever, AOR, 1.55; 95% CI, 1.14-2.11; diarrhea, AOR, 1.80; 95% CI, 1.19-2.74; and constipation, AOR, 1.25; 95% CI, 0.88-1.78) as well as patients with a comorbidity index of 2 or greater (adults, abdominal pain, AOR, 3.33; 95% CI, 3.09-3.60; nausea and/or vomiting, AOR, 3.66; 95% CI, 3.23-4.14; fever, AOR, 5.00; 95% CI, 3.79-6.60; diarrhea, AOR, 4.27; 95% CI, 3.39-5.38; and constipation, AOR, 4.17; 95% CI, 3.08-5.65; children, abdominal pain, AOR, 2.42; 95% CI, 1.93-3.05; nausea and/or vomiting, AOR, 2.55; 95% CI, 1.89-3.45; fever, AOR, 4.12; 95% CI, 2.71-6.25; diarrhea, AOR, 2.17; 95% CI, 1.18-3.97; and constipation, AOR, 2.19; 95% CI, 1.30-3.70) were more likely to have missed appendicitis. Adult patients who received computed tomographic scans at the initial ED visit (abdominal pain, AOR, 0.58; 95% CI, 0.52-0.65; nausea and/or vomiting, AOR, 0.63; 95% CI, 0.52-0.75; fever, AOR, 0.41; 95% CI, 0.29-0.58; diarrhea, AOR, 0.83; 95% CI, 0.58-1.20; and constipation, AOR, 0.60; 95% CI, 0.39-0.94) were less likely to have missed appendicitis. Conclusions and Relevance: Regardless of age, a missed diagnosis of appendicitis was more likely to occur in women, patients with comorbidities, and patients who experienced abdominal pain accompanied by constipation. Population-based estimates of the rates of potentially missed appendicitis reveal opportunities for improvement and identify factors that may mitigate the risk of a missed diagnosis.