Interim Report of the Committee on Geographic Variation in Health Care Spending and Promotion of High-Value Health Care: Preliminary Committee Observations is designed to provide the committee's preliminary observations for the 113th Congress as it considers further Medicare reform. This report contains only key preliminary observations related primarily to the committee's commissioned analyses of Medicare Parts A (Hospital Insurance program), B (Supplementary Medical Insurance program) and D (outpatient prescription drug benefit), complemented by other empirical investigations. It does not contain any observations related to the committee's commissioned analyses of the commercial insurer population, Medicare Advantage, or Medicaid, which will be presented in the committee's final report after completion of quality-control activities. This interim report excludes conclusions or recommendations related to the committee's consideration of the geographic value index or other payment reforms designed to promote highvalue care. Additional analyses are forthcoming, which will influence the committee's deliberations. These analyses include an exploration of how Medicare Part C (Medicare Advantage) and commercial spending, utilization, and quality vary compared with, and possibly are influenced by, Medicare Parts A and B spending, utilization, and quality. The committee also is assessing potential biases that may be inherent to Medicare and commercial claims-based measures of health status. Based on this new evidence and continued review of the literature, the committee will confirm the accuracy of the observations presented in this interim report and develop final conclusions and recommendations, which will be published in the committee's final report.