The objective of this study was to evaluate the payment implications of substituting the Minimum Data Set-Post Acute Care (MDS-PAC) for the FIM™ instrument for use in the planned prospective payment system (PPS) for inpatient rehabilitation hospitals. FIM™ is a trademark of the Uniform Data System for Medical Rehabilitation, a division of UB Foundation Activites, Inc.
We used a prospective cross-sectional design using consecutive sampling.
We studied all Medicare admissions with stays of 3 days or more over a 2-month period to 50 inpatient rehabilitation hospitals in 22 states.
Measurements and Methods
Each participating institution completed both the FIM and the MDS-PAC assessments on all participants. Items from the MDS-PAC were combined and translated to create “FIM-like” items. We assessed agreement of classification into prospective payment cells using FIM assessment data and also using MDS-PAC data. Statistical adjustments were applied to improve the level of agreement.
The mean differences between the FIM motor and cognitive scales and their MDS-PAC translations were 2.4 (mean = 45) and 0.0 (mean = 28), respectively, with scale correlations of .85 and .84. Weighted kappas on individual items ranged from .32 to .64. There were substantial hospital-specific differences in scoring. Payment cell classification using FIM data agreed with that using MDS-PAC data only 56% of the time. Twenty percent of the facilities experienced revenue shifts larger than 10%.
Despite better item-level agreement than previously observed, poor payment cell agreement and substantial revenue shifts indicated that the MDS-PAC should not be substituted for the FIM™ instrument in the rehabilitation hospital PPS.