Higher CMG assignment (1003) was also associated with lower probabilities of discharge to the community compared to patients assigned to lower CMGs (1001 and 1002).
Secondly, the data were limited to the years following substantial changes in the way CMGs for amputation being determined.
Case mix groups (CMGs) are calculated from weighted admission FIM motor ratings: CMG 1001 (FIM motor greater than 47.65), CMG 1002 (FIM motor greater than 36.25 and less than 47.65), and CMG 1003 (FIM motor less than 36.25).
The basis for reimbursement under the IRF prospective payment system is a patient's impairment-specific case mix group (CMG).
Two multiple linear regression models were constructed to determine the impact of independent variables (CMG and amputation level) on predicting rehabilitation outcomes (LOS and discharge functional rating) while controlling for other demographic and health characteristics (covariates).
Without adjusting for other covariates, patients with bilateral transfemoral level of amputation under CMG 1003 had the highest LOS (13.7 days) as compared to patients with other levels of amputation and CMG.
CMG was strongly associated with all three outcomes; significant differences were observed between each CMG level.