Purpose: We used the example of colonoscopy to explore how coverage decisions influence health care. The Medicare program did not cover screening colonoscopy for individuals at average risk for colorectal cancer until 2001, and many private insurers do not cover such screening. Previous studies showed a dramatic increase in colonoscopy use after the Medicare coverage, although these studies did not use nationally representative data, did not control for temporal trends, and did not examine the resultant costs and benefits.

The purpose of this study was to: (1) Examine trends in colonoscopy use and insurer coverage between 2000-2003, during which time Medicare began covering colonoscopy for screening purposes (2) Examine the impact of these trends on health outcomes and costs (3) Explore the role of insurer reimbursement and health policies - particularly Medicare coverage - in facilitating use of preventive health services.

Methods: We used nationally representative data from the 2000 and 2003 National Health Interview Surveys and a previously developed cost-effectiveness model (Uri Ladabaum et al).

Results: We found that colonoscopy use increased from 23% in 2000 to 33% in 2003 in the Medicare population and from 17%-27% in the insured non-Medicare population (p=.03 for both). Overall screening utilization and adherence to guidelines also increased. We found that colonoscopy use was significantly higher for Medicare enrollees than non-Medicare, insured individuals in 2003 (p=.04) but not in 2000 (p=.11). The observed use of screening in 2003 was relatively more cost-effective than in 2001, as it improved health outcomes although at a higher cost.

Conclusions: We found that insurer coverage may increase the use of preventive health care services. Our findings raise broader issues for other health care services about how such coverage decisions are made. Our presentation will also discuss the intersection of science and politics in coverage decisions.