Cost-effectiveness of computed tomography and ultrasound in the diagnosis of appendicitis.

INTRODUCTION Diagnosis of acute appendicitis is difficult in nearly 30% of patients with pain in low right quadrant. Diagnostic imaging may provide a means of a more accurate diagnosis. OBJECTIVE The cost-effectiveness of diagnostic image tests was calculated for comparison with routine physical examination in patients with abdominal pain suspected to be appendicitis. MATERIALS AND METHODS A cost-effectiveness protocol was designed, using a decision analysis model. The standard case was a patient with abdominal pain in right lower quadrant and suspicion of appendicitis. Three independent diagnostic alternatives were selected--ultrasonography, abdominal tomography and physical exam in hospital with the subject under observation less than six hours. Operative characteristics, study design and costs of interventions and outcomes were assessed. The main outcome consisted of a confirmed diagnosis of appendicitis. The point of view taken was that of health maintenance organizations. Direct and indirect medical costs were measured. Time horizon used was three months. A one way sensitivity analysis was made. RESULTS For a prepaid system, the most cost-effective strategy was abdominal tomography, with a cost-effectiveness ratio of US$965/diagnosed patient. For public system, the most cost-effective strategy was abdominal tomography, with a cost-effectiveness ratio of US$492/diagnosed patient. CONCLUSIONS Imaging diagnostic methods, in cases of abdominal pain suspected to be appendicitis, are more cost-effective than physical exam to make accurate diagnostic decisions. Tomography offers the best cost-effectiveness in prepaid system and in public health system.