Initial home health outcomes under prospective payment

Health Services Research, Feb, 2005 by Robert E. Schlenker, Martha C. Powell, Glenn K. Goodrich

Some OASIS items are used both to determine the HHRG for payment and as risk factors in the CMS outcome models. Since financial incentives may influence how HHRG-related OASIS items are reported by agencies (although the extent of any such "gaming" is unknown), a strength of the CMS outcome models is that they include as risk factors a considerable number of OASIS items beyond those used for HHRG determination. The variables shown in Table 1 for improvement in ambulation/locomotion are illustrative. Of the 37 risk factors, only nine are used for HHRG determination and six more are related to items used for HHRGs. The remaining 22 risk factors are not used in determining payment.

Sample and Data Sources

We selected a random sample of episodes for each period in order to compare representative pre-PPS to PPS outcomes. The pre-PPS sample covers episodes beginning during October December 1999 and ending prior to April 1, 2000. This time period allowed for the initial data inaccuracies in OASIS collection and transmission by home health agencies to have been overcome. It also occurred sufficiently before the start of PPS to minimize anticipatory practice changes that agencies may have undertaken in advance of PPS. The PPS sample covers the entire calendar year 2001. To check for possible seasonal variations that might affect the comparability of the two time periods, comparisons of the OASIS data for each calendar quarter in 2001 were made and no major differences were found.

Data on outcomes, risk factors, visits, and HHRGs were derived from OASIS information in the CMS national OASIS repository and Medicare claims data. The analysis focused on the impact of PPS on "mainstream" Medicare patients (i.e., age 65 years and older) receiving home health care under per-episode PPS payment. This required several exclusions from the universe of episodes. OASIS data on Medicare home health patients age 65 and older were randomly sampled from the CMS national OASIS repository. Several million OASIS assessments are included in the repository for each year. We initially sampled about 270,000 outcome episodes for the pre-PPS period and 50,000 episodes for the 2001 PPS period. (A larger pre-PPS sample was selected to meet analysis needs beyond those covered in this article.) Managed care patients were excluded because they do not come under PPS payment. Patients who died while in home health care and nonresponsive patients also were excluded, because such patients are not included in the CMS outcome reports. The outcome episodes from the OASIS data were then matched with Medicare claims data. Not all episodes could be matched because of inconsistencies in Medicare numbers and, for the pre-PPS period, a lack of precise service dates in the claims data. The match rates were 84 percent pre PPS and 93 percent PPS. To check for possible biases resulting from the lower match rate for the pre PPS period, we compared case mix between the matched and unmatched pre-PPS episodes (based on OASIS data) and found only minimal differences.