Should Medical Severity-Diagnosis Related Group Classification Be Utilized for Reimbursement? An Analysis of Elixhauser Comorbidities and Cost of Care

Area of Science:

• Orthopedic Surgery
• Health Economics
• Medical Informatics

Background:

• The Center for Medicare and Medicaid Services (CMS) uses MS-DRGs 469 and 470 for reimbursement of total hip arthroplasty (THA) and total knee arthroplasty (TKA).
• The Elixhauser comorbidity index, comprising 31 variables, is used to identify patients with major complications or comorbidities (MS-DRG 469).
• This study questions whether the Elixhauser comorbidities are the most accurate predictors of increased healthcare costs in arthroplasty patients.

Purpose of the Study:

• To evaluate the correlation between Elixhauser comorbidities, MS-DRG 469 classification, and actual cost of care in THA and TKA patients.
• To identify which comorbidities are most predictive of increased complexity classification versus true increased cost.

Main Methods:

• Retrospective analysis of 1243 TKAs and 897 THAs from 2013 to 2017.
• Univariable and multivariable logistic regression analyses were performed on Elixhauser comorbidities.
• Investigation focused on variables associated with MS-DRG 469 and increased cost of care.

Main Results:

• Only 1.8% of patients were classified as MS-DRG 469.
• Coagulopathy, electrolyte disorders, neurodegenerative disorders, and psychosis were significantly associated with MS-DRG 469 classification.
• While these four comorbidities increased costs, 13 other comorbidities also predicted higher costs without affecting MS-DRG classification.

Conclusions:

• There is a weak correlation between the current MS-DRG 469 classification and the actual cost of care for THA and TKA.
• The existing risk adjustment system by CMS may not adequately capture the true financial burden associated with patient comorbidities.
• An expanded risk adjustment system is needed for THA and TKA reimbursement to better reflect patient complexity and associated costs.