653 Cost-Effectiveness of Alternative Diagnostic Strategies for Patients with Suspected Small-Bowel Crohn's Disease

Abstract

Background: The cost-effectiveness of alternative approaches to the diagnosis of Crohn's disease is unknown. Objective: To evaluate the cost-effectiveness (CE) of ileocolonoscopy, small-bowel follow-through (SBFT), CT enterography (CTE), and capsule endoscopy for the diagnosis of small-bowel Crohn's disease. Methods: A Markov model was developed to compare the life-time costs and benefits of each diagnostic strategy for a cohort of suspected Crohn's disease patients using a societal perspective. Test characteristics, disease natural history parameters, costs, and utilities were estimated from the literature and Medicare reimbursement rates. Effectiveness was measured in quality-adjusted life-years (QALYs) gained. All assumptions were tested with sensitivity analyses. Results: The cost-effectiveness of strategies depended critically on the pretest probability of Crohn's disease and whether or not the terminal ileum is successfully examined at ileocolonoscopy. For patients with a pretest probability of less than 70%, the strategy of CTE after a negative ileocolonoscopy with ileal biopsies had an incremental CE ratio exceeding $100,000 per QALY-gained. CTE dominated SBFT. When colonoscopy failed to intubate the terminal ileum, using SBFT to follow-up of any patient with pretest probability greater than 20% had a CE ratio of less than $100,000 per QALY-gained. The incremental CE of performing CTE instead of SBFT for these patients was greater than $100,000 per QALY-gained unless the pretest probability of Crohn's disease surpassed 70%. Capsule endoscopy cost more than $500,000 per QALYgained when performed as a follow-up to negative SBFT or negative CTE, even in patients with high (80%) pretest probabilities of Crohn's disease. Our results were sensitive to the diagnostic accuracy of the tests and the life-time cost of misdiagnosing a patient with disease. Threshold analysis revealed that if a new test had a conditional sensitivity after ileocolonoscopy greater than 60% and a specificity greater than 98% its cost-effectiveness ratio would be less than $100,000 per QALY-gained at a test cost of $5000. It is not yet known if MR-enterography or double-balloon enteroscopy will have these, or better, test characteristics. Conclusion: CTE and SBFT are cost-effective additions to ileocolonoscopy only in selected patients with suspected Crohn's disease. After a negative ileocolonoscopy with ileal biopsies, CTE is a cost-effective follow-up diagnostic only when there is a greater than 70% chance that the patient has Crohn's disease. The low specificity of capsule endoscopy makes it expensive relative to other diagnostic technologies.