The Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project (HCUP) consists of a national inpatient database containing 100 percent of the inpatient claims from a sample of hospitals in 24 states. Although the sampling frame is limited to participating states, it is selected to reflect characteristics of community hospitals nationwide. Weights are provided that can be used to produce national and regional estimates or state estimates for the participating states. We used the 1998 HCUP data in our analyses.
The HCUP files contain more than 100 clinical and non-clinical variables included in a hospital inpatient discharge abstract, including diagnostic information, patient demographics, length of stay, and--most important for this project--total charges and expected primary and secondary payment source (such as Medicare/Medicaid/private insurance/self-pay). The HCUP data can be used to develop measures of inpatient hospital utilization and case mix by payer class. The charge data can be used with cost-to-charge ratios from the Medicare cost reports to compute costs by payer category for each hospital. Payment amounts are not provided. The sampling means that the data cannot be used to develop measures of market share for specific hospitals
In addition to the national inpatient database, each participating state maintains a State Inpatient Database (SID). The SID contains data on all discharges from all community hospitals in the participating states. We used the 1997 SID for three states in our exploratory analyses: California, New York, and Wisconsin.
There is no comparable database for outpatient services that provides utilization data by payer.4
4. Nine states provide information on ambulatory surgery that includes payer information.