False-negative and false-positive errors in abdominal pain evaluation: Failure to diagnose acute appendicitis and unnecessary surgery

Objectives: To test the hypothesis that physician errors (failure to diagno se appendicitis at initial evaluation) correlate with adverse outcome. The authors also postulated that physician errors would correlate with delays i n surgery, delays in surgery would correlate with adverse outcomes, and phy sician errors would occur on patients with atypical presentations. Methods: This was a retrospective two-arm observational cohort study at 12 acute ca re hospitals: 1) consecutive patients who had an appendectomy for appendici tis and 2) consecutive emergency department abdominal pain patients. Outcom e measures were adverse events (perforation, abscess) and physician diagnos tic performance (false-positive decisions, false-negative decisions). Resul ts: The appendectomy arm of the study included 1,026 patients with 110 (10. 5%) false-positive decisions (range by hospital 4.7% to 19.5%). Of the 916 patients with appendicitis, 170 (18.6%) false-negative decisions were made (range by hospital 10.6% to 27.8%). Patients who had false-negative decisio ns had increased risks of perforation (r = 0.59, p = 0.058) and of abscess formation (r = 0.81, p = 0.002). For admitted patients, when the inhospital delay before surgery was >20 hours, the risk of perforation was increased [2.9 odds ratio (OR) 95% CI = 1.8 to 4.8]. The amount of delay from initial physician evaluation until surgery varied with physician diagnostic perfor mance: 7.0 hours (95% CI = 6.7 to 7.4) if the initial physician made the di agnosis, 72.4 hours (95% CI = 51.2 to 93.7) if the initial office physician missed the diagnosis, and 63.1 hours (95% CI = 47.9 to 78.4) if the initia l emergency physician missed the diagnosis. Patients whose diagnosis was in itially missed by the physician had fewer signs and symptoms of appendiciti s than patients whose diagnosis was made initially [appendicitis score 2.0 (95% CI = 1.6 to 2.3) vs 6.5 (95% CI = 6.4 to 6.7)]. Older patients (>41 ye ars old) had more false-negative decisions and a higher risk of perforation or abscess (3.5 OR 95% CI = 2.4 to 5.1). False-positive decisions were mad e for patients who had signs and symptoms similar to those of appendicitis patients [appendicitis score 5.7 (95% CI = 5.2 to 6.1) vs 6.5 (95% CI = 6.4 to 6.7)]. Female patients had an increased risk of false-positive surgery (2.3 OR 95% CI = 1.5 to 3.4). The abdominal pain arm of the study included 1,118 consecutive patients submitted by eight hospitals, with 44 patients h aving appendicitis. Hospitals with observation units compared with hospital s without observation units had a higher "rule out appendicitis" evaluation rate [33.7% (95% CI = 27 to 38) vs 24.7% (95% CI = 23 to 27)] and a simila r hospital admission rate (27.6% vs 24.7%, p = NS). There was a lower miss- diagnosis rate (15.1% vs 19.4%, p = NS power 0.02), lower perforation rate (19.0% vs 20.6%, p = NS power 0.05), and lower abscess rate (5.6% vs 6.9%, p = NS power 0.06), but these did not reach statistical significance. Concl usions: Errors in physician diagnostic decisions correlated with patient cl inical findings, i.e., the missed diagnoses were on appendicitis patients w ith few clinical findings and unnecessary surgeries were on non-appendiciti s patients with clinical findings similar to those of patients with appendi citis. Adverse events (perforation, abscess formation) correlated with phys ician false-negative decisions.