WHI-Medicare linkage

1. WHI-Medicare linkage Beth Virnig, Ph.D., MPH virni001@umn.edu 612-624-4426

2. When to use the linkage? • When the scientific product using both data sources is superior to that based on one alone • When the scientific product is only possible when using both data sources (the question cannot be answered using either data source alone)

3. What sorts of benefits does Medicare data provide? • Follow-up for all persons who are in the Medicare program (no non-response bias) • Consistent reporting across hospitals, clinics, etc. • Diagnoses • Procedures • Dates • Different sources of care

4. What are the limitations of Medicare? • Results of lab tests • Conditions that aren’t diagnosed or with a missed diagnosis won’t be diagnosed in the Medicare data. Likewise, misdiagnosis is not corrected • Clinical intent isn’t known (we don’t know why, just that it was done) • Details for hospitalizations are limited to big-ticket items • Managed Care Enrollees won’t have detailed data • Few people have any information prior to the month before they turn 65

5. Key steps for using the Medicare linkage • Limit to women in both datasets • Often limit to age 65 and older • Remove (or censor) people in managed care • Consider, the different definitions used by Medicare and WHI • WHI only measures the first event (stroke, etc), Medicare will measure all events • WHI relies on self-report to initiate process • Adding outcomes not based on Medicare is only done prospectively. A Medicare-based definition can be applied retrospectively • Medicare does not measure behaviors, clinical severity, etc. well