Identifying Observation Stays in Medicare Data: Policy Implications of a Definition
Observation stays are increasingly common, yet no standard method to identify observation stays in Medicare claims is available, including events with status change. To determine the claims patterns of Medicare observation stays, define comprehensive claims-based methodology for future Medicare observation research and data reporting, and identify policy implications of such definition, we identified potential observation events in a 2014 20% random sample of Medicare beneficiaries with both Part A and B claims and at least 1 acute care stay (1,667,660 events). Observation revenue center (ORC) and Healthcare Common Procedure Coding System codes occurring within 30 days of an inpatient hospitalization were recorded. A total of 125,920 (7.6%) events had an ORC code, and 75,502 (4.5%) were in the outpatient revenue center. Claims patterns varied tremendously, and almost half (47.3%, 59,529) of the ORC codes were associated with an inpatient claim, indicating status change and demonstrating a need for clarity in observation policy. The proposed University of Wisconsin method identified 72,858 of 75,502 (96.5%) events with ORC codes as observation stays, and provides a comprehensive, reproducible methodology. Funding: National Institute on Minority Health and Health Disparities of the National Institutes of Health under Award Number R01MD010243.
© 2019 Society of Hospital Medicine
Medicare observation stays are increasingly common. From 2006 to 2012, Medicare observation stays increased by 88%,1 whereas inpatient discharges decreased by 13.9%.2 In 2012, 1.7 million Medicare observation stays were recorded, and an additional 700,000 inpatient stays were preceded by observation services; the latter represented a 96% increase in status change since 2006.1 Yet no standard research methodology for identifying observation stays exists, including methods to identify and properly characterize “status change” events, which are hospital stays where initial and final inpatient or outpatient (observation) statuses differ.
With the increasing number of hospitalized patients classified as observation, a standard methodology for Medicare claims research is needed so that observation stays can be consistently identified and potentially included in future quality measures and outcomes. Existing research studies and government reports use widely varying criteria to identify observation stays, often lack detailed methods on observation stay case finding, and contain limited information on how status changes between inpatient and outpatient (observation) statuses are incorporated. This variability in approach may lead to omission and/or miscategorization of events and raises concern about the comparability of prior work.
This study aimed to determine the claims patterns of Medicare observation stays, define comprehensive claims-based methodology for future Medicare observation research and data reporting, and identify policy implications of such definition. We are poised to do this work because of our access to the nationally generalizable Centers for Medicare & Medicaid Services (CMS) linked Part A inpatient and outpatient data sets for 2013 and 2014, as well as our prior expertise in hospital observation research and Medicare claims studies.
METHODS
General Methods and Data Source
A 2014 national 20% random sample Part A and B Medicare data set was used. In accordance with the Centers for Medicare & Medicaid (CMS) data use agreement, all included beneficiaries had at least 1 acute care inpatient hospitalization. Included beneficiaries were enrolled for 12 months prior to their first 2014 inpatient stay. Those with Medicare Advantage or railroad benefits were excluded because of incomplete data per prior methods.3 The University of Wisconsin Institutional Review Board approved this study.
Comparison of Methods
The PubMED query “Medicare AND (observation OR observation unit),” limited to English and publication between January 1, 2010 and October 1, 2017, was conducted to determine the universe of prior observation stay definitions used in research for comparison (Appendix).4-20 The Office of Inspector General report,21 the Research Data Assistance Center (ResDAC),22 and Medicare Claims Processing Manual (MCPM)23 were also included. Methods stated in each publication were used to extrapolate observation stay case finding to the study data set.
