Scoring system to distinguish uncomplicated from complicated acute appendicitis

Non-operative management may be an alternative for uncomplicated appendicitis, but preoperative distinction between uncomplicated and complicated disease is challenging. This study aimed to develop a scoring system based on clinical and imaging features to distinguish uncomplicated from complicated appendicitis. Patients with suspected acute appendicitis based on clinical evaluation and imaging were selected from two prospective multicentre diagnostic accuracy studies (OPTIMA and OPTIMAP). Features associated with complicated appendicitis were included in multivariable logistic regression analyses. Separate models were developed for CT and ultrasound imaging, internally validated and transformed into scoring systems. A total of 395 patients with suspected acute appendicitis based on clinical evaluation and imaging were identified, of whom 110 (27·8 per cent) had complicated appendicitis, 239 (60·5 per cent) had uncomplicated appendicitis and 46 (11·6 per cent) had an alternative disease. CT was positive for appendicitis in 284 patients, and ultrasound imaging in 312. Based on clinical and CT features, a model was created including age, body temperature, duration of symptoms, white blood cell count, C-reactive protein level, and presence of extraluminal free air, periappendiceal fluid and appendicolith. A scoring system was constructed, with a maximum possible score of 22 points. Of the 284 patients, 150 had a score of 6 points or less, of whom eight (5·3 per cent) had complicated appendicitis, giving a negative predictive value (NPV) of 94·7 per cent. The model based on ultrasound imaging included the same predictors except for extraluminal free air. The ultrasound score (maximum 19 points) was calculated for 312 patients; 105 had a score of 5 or less, of whom three (2·9 per cent) had complicated appendicitis, giving a NPV of 97·1 per cent. With use of novel scoring systems combining clinical and imaging features, 95 per cent of the patients deemed to have uncomplicated appendicitis were correctly identified as such. The score can aid in selection for non-operative management in clinical trials