Diagnostic decision support in suspected acute appendicitis: Validation of a simplified scoring system

Objective: To validate a simplified scoring system as an aid to the diagnosis of acute appendicitis. Design: Open prospective study. Setting: County district hospital, and university hospital, Sweden. Subjects: 1167 Patients with suspected appendicitis. Main outcome measures: Correlation between scoring system and final diagnosis. Results: A total of 475 patients were operated on and 392 (82.5%) of these had histologically verified appendicitis. The negative laparotomy rate was 17.5% (11.2% for men and 25.4% for women). The sensitivity of the scoring system for appendicitis at the main cut-off point (score -2 or more) was 0.73 and the specificity was 0.87. At the cut-off level (score -17 or less) for predicting non-specific abdominal pain (NSAP) the proportion of correctly classified patients was 0.72 and the proportion of false negatives (patients with appendicitis classified as NSAP) was 0.14. Analysis of the area under the receiver operating characteristic (ROC) curve showed that the scoring system performed slightly worse in the university hospital (area 0.83) than in the district hospital where it was originally developed (area 0.89). Conclusion: The scoring system was a valid instrument for discriminating between acute appendicitis and NSAP in the two centres studied. Use of the scoring system in daily clinical work was associated with a reduced rate of negative laparotomies.