Artificial Intelligence based detection of pneumoperitoneum on CT scans in patients presenting with acute abdominal pain: A clinical diagnostic test accuracy study

•An AI algorithm can detect pneumoperitoneum in abdominal CT scans.•Results demonstrated low sensitivity and a very high specificity.•Not suitable as stand-alone screening layer.•Does not cause disruptive false alerts in existing workflows.•Early warning can help accelerate life-saving treatment for acutely ill patients. The primary aim was to investigate the diagnostic performance of an Artificial Intelligence (AI) algorithm for pneumoperitoneum detection in patients with acute abdominal pain who underwent an abdominal CT scan. This retrospective diagnostic test accuracy study used a consecutive patient cohort from the Acute High-risk Abdominal patient population at Herlev and Gentofte Hospital, Denmark between January 1, 2019 and September 25, 2019. As reference standard, all studies were rated for pneumoperitoneum (subgroups: none, small, medium, and large amounts) by a gastrointestinal radiology consultant. The index test was a novel AI algorithm based on a sliding window approach with a deep recurrent neural network at its core. The primary outcome was the area under the curve (AUC) of the receiver operating characteristic (ROC). Of 331 included patients (median age 68 years (Range 19–100; 180 women)) 31 patients (9%) had pneumoperitoneum (large: 16, moderate: 7, small: 8). The AUC was 0.77 (95% CI 0.66–0.87). At a specificity of 99% (297/300, 95% CI: 97–100%), sensitivity was 52% (16/31, 95% CI 29–65%), and positive likelihood ratio was 52 (95% CI 16–165). When excluding cases with smaller amounts of free air (