Background: Acute appendicitis is one of the main causes of abdominal pain that requires surgical treatment, it occurs at any stage of life with a lifetime risk of 7% in general population; clinical findings are usually sufficient to make diagnosis, but definitive diagnosis is made at the moment of surgery; there isn´t a reliable marker of acute apendicitis but it has been hypothesized that serum bilirrubin levels increase in complicated appendicitis cases and that it can be measured before appendectomy to predict severity levels. Objective: To determine if the increase in serum bilirrubin levels has a positive predictive value of severity in patients with acute appendicitis. Material and methods: Observational, prospective and analytical cross-sectional study in patients diagnosed with acute appendicitis, who attended the Emergency Department to identify the positive predictive value of bilirubin. Bilirubin levels were determined by obtaining a cut-off point greater than 1.0 mg/dl for total bilirubin, >0.8 mg/dl for indirect bilirubin and >0.2 for direct bilirubin; considering the standard Gold the diagnosis with the intraoperative macroscopic findings. Sampling was random and the sample size was probabilistic. It was analyzed with descriptive statistics in addition to diagnostic tests with 95% CI, using the statistical package SPSS. Results: 59 patients with acute appendicitis were selected, mean age 34.4 ± 14.3 years, 34 (58%) were female, 20 (33.9%) were overweight, 4 (6.8%) had arterial hypertension. Of the complications corresponded to abscess and perforation in 9 (31%), perforation with 8 (27.6%). The severity of the episodes of acute appendicitis occurred in 41 (69%). The effectiveness of bilirubins to detect severity, showed in the total with 82% (95% CI 64-92), the direct 73% (95% CI 58-84), indirect in 62% (95% CI 31-83) . The discriminative capacity of indirect bilirubin with 0.52, the direct one with 0.44 and total with 0.35. Conclusions: total bilirubin has a higher positive predictive value of severity in patients with acute appendicitis and the indirect higher discriminative value.
