The primary data source for this study was the 2006 Medicare claims data that provided information on utilization and Medicare payments associated with each hospital discharge and post-acute care episode. Two other data sources were examined for their use in determining the nature of organizational relationships between hospitals and PAC providers. These sources were the Hospital Cost Report Information System (HCRIS) and the Online Survey and Certification Reporting System (OSCAR).
Medicare Claims Data. The 2006 Medicare claims files were used to track patterns of post-acute care use, including PAC service mix, length of stay, payment, and acute hospital readmission rates. The Medicare claims files were used to build episodes of acute plus PAC using inpatient acute, IRF, LTCH, SNF, HHA, and outpatient therapy claims. Note that inpatient acute claims included both prospective payment system (PPS) and critical access hospital (CAH) claims. The individual DRG numbers discussed throughout this paper refer to the FY 2006 CMS DRG system. Although they were not part of the episode definition, we also assigned Medicare carrier claims (including physician services, independent clinical laboratories, ambulance providers, and freestanding ambulatory surgery centers), hospice, and DME claims to the episodes based on dates of service in order provide a more comprehensive understanding of the resources associated with beneficiary care during PAC episodes. Medicare claims were also used to examine transfer patterns within PAC episodes to learn more about factors predicting first site of care after an acute hospital discharge and subsequent settings of care in a PAC episode. Using Medicare inpatient admission claims, we applied case mix measures to the PAC episodes using the 3M Health Information Systems APR-DRG and the newly developed MS-DRG software to assign severity of illness measures to index hospitalizations. The APR-DRG and MS-DRG groupers were used to distinguish beneficiary severity level at index acute hospitalization. Medicare inpatient claims data were also used to identify comorbid conditions, as defined by the Hierarchical Conditions Categories (HCCs) software. The use of APR-DRGs, MS-DRGs, and use of HCCs is explained further in Section 2.4.2.
Online Survey and Certification Reporting System (OSCAR). The 2007 OSCAR database contains information on facility characteristics including ownership, bed capacity, and rural versus urban location. These facility characteristics have been used in both descriptive and multivariate analysis. The OSCAR data were the source for initial geographic analyses looking at the distribution of different types of post-acute providers by state. The OSCAR data were also used to identify colocated providers using the provider address reported in the OSCAR files. After geocoding the addresses in the OSCAR data to identify the latitude and longitude of each provider, RTI used geographic information systems (GIS) to identify colocated facilities, defined as those within 250 yards of each other. This definition of co-location is consistent with regulations defining colocated LTCHs. However, because the OSCAR data typically report corporate addresses and not individual provider addresses, we suspect the colocation factor is under-reported in our analyses.
Hospital Cost Report Information System (HCRIS). The HCRIS files (FY 2005-2006) are available for hospitals, hospices, renal dialysis facilities, SNFs, and HHAs. Facility identification numbers (IDs) for wholly owned hospital-based PAC settings were identified from the parent institutions' files and linked to provider IDs in the Medicare claims episode of care files. By linking provider IDs in this way, we were able to track referral patterns to related hospital-based subproviders. RTI explored using the OSCAR files versus the HCRIS data to identify hospital-based subproviders and found that the HCRIS data were more reliable than the OSCAR data for this purpose. Subproviders have formal ownership relationships that must be reported in the HCRIS data.