CRP and appendicitis: Participants aged 18–65 years were diagnosed by AIR score and adjunctive abdominal ultrasound in selected participants. Participants with intermediate probability of acute appendicitis from AIR score were examined with abdominal ultrasound and were included in the study if ultrasound findings confirmed the clinical suspicion of acute appendicitis. Participants with high probability of acute appendicitis from AIR score without signs of perforation and with WCC of less than 15 000/μl and CRP less than 5 mg/l were included for the randomization.