Correlation of peritoneal aspiration cytology with acute appendicitis.

Fifty-one patients in whom a clinical diagnosis of acute appendicitis had been made underwent peritoneal aspiration cytology (PAC). Thirty-six had a positive result, 11 had a negative result and aspiration failed in four cases. All patients had an appendicectomy and the histological findings were correlated with the PAC results. Thirty-five of the 36 patients with a positive PAC had histologically proven appendicitis. Seven of the 11 patients with a negative result had normal appendices. The sensitivity of PAC for acute appendicitis was 85% and the specificity was 70%. The positive predictive value was found to be 97% and the negative predictive value 60%. Peritoneal aspiration cytology is a useful aid in the diagnosis of acute appendicitis however, a negative result does not exclude this diagnosis.