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Acute Appendicitis in Young Children: Cost-effectiveness of US versus CT in Diagnosis—A Markov Decision Analytic Model¹

¹ From the Department of Diagnostic Imaging (M.J.W., E.Ç., A.S.D.), Division of Child Health Evaluative Sciences (W.J.U.), and Department of Haematology/Oncology (L.S.), the Hospital for Sick Children, 555 University Ave, Toronto, ON, Canada M5G 1X8; the Division of Clinical Decision-Making and Health Care, Toronto General Research Institute, Toronto, Ontario, Canada (M.K.); and the Department of Radiology, Miami Children's Hospital, Miami, Fla (L.S.M.). From the 2007 RSNA Annual Meeting. Received January 15, 2008; revision requested February 28; revision received August 8; accepted September 2; final version accepted September 3. A.S.D. supported by a Canadian Child Health Clinician-Scientist Program Career Development Award and by a Department of Medical Imaging of the University of Toronto Faculty Development Award. Address correspondence to A.S.D.(e-mail: andrea.doria{at}sickkids.ca).

Purpose: To compare the cost-effectiveness of different imaging strategies in the diagnosis of pediatric appendicitis by using a decision analytic model.

Materials and Methods: Approval for this retrospective study based on literature review was not required by the institutional Research Ethics Board. A Markov decision model was constructed by using costs, utilities, and probabilities from the literature. The risk of radiation-induced cancer was modeled by using the Biological Effects of Ionizing Radiation VII report, which is based primarily on data from atomic bomb survivors. The three imaging strategies were ultrasonography (US), computed tomography (CT), and US followed by CT if the initial US study was negative. The model simulated the short-term and long-term outcomes of the patients, calculating the average quality-adjusted life span and health care costs.

Results: For a single abdominal CT study in a 5-year-old child, the lifetime risk of radiation-induced cancer would be 26.1 per 100 000 in female and 20.4 per 100 000 in male patients. In the base-case analysis, US followed by CT was the most costly and most effective strategy, CT was the second-most costly and second-most effective strategy, and US was the least costly and least effective strategy. The incremental cost-effectiveness ratios (ICERs) of CT to US and of US followed by CT to US were both well below the societal willingness-to-pay threshold of $50 000 (in U.S. dollars). The ICER of US followed by CT to CT was less than $10 000 in both male and female patients.

Conclusion: In a Markov-based decision model of pediatric appendicitis, the most cost-effective method of imaging pediatric appendicitis was to start with a US study and follow each negative US study with a CT examination.

© RSNA, 2008