To the Editor.
—Dr Green and colleagues1 describe the limitations of the ranking method used by US News & World Report in their annual survey of "America's Best Hospitals." One component of that ranking is adjusted hospital mortality rates. As the authors point out, concerns about the methods used to make case-mix adjustments in hospital mortality rates led the Health Care Financing Administration (HCFA) to discontinue public release of Medicare hospital mortality rates in 1993. US News & World Report continued to rely on HCFA's published 1991 hospital mortality rates until 1994. Since then, US News & World Report has had a contractor develop casemix-adjusted hospital mortality rates using HCFA's publicly released Medicare claims data.2However, there is a fundamental difference between the Medicare claims data now released by HCFA and the data HCFA used to computed hospital mortality rates before 1993. In their internal analyses, HCFA matched Medicare claims data to Social Security records.