Content Link: MS-DRGs and CMI
- Calculate the Case Mix Index for a selected group of cases.
- Analyze Case Mix Indices for different facilities.
- Evaluate the impact of utilization patterns on a facility’s Case Mix.
The case mix of a patient population is a description of that population based on any number of the following characteristics such as age, gender, treatments received or resources used. Case Mix Analysis is used to determine reimbursement, to describe a population being served and to identify differences in practice patterns or coding complexity.
The case mix index is the average of the relative weights of all cases treated at a given facility. The theoretical average CMI is 1.000. CMI’s over 1.000 signify more complex cases and CMI’s less than 1.000 signify less complex cases. Factors that influence a facility’s case mix index include:
- Changes made in relative weight values
- Changes in the type of services offered or provided by the facility
- Accuracy of documentation and coding in MS-DRG or APC assignment
Case Mix Analysis begins with the calculation of the Case Mix Index. The Case-Mix Index is the average of the relative weights of all cases treated at a given facility or by a given physician. The formula for calculating the Case Mix Index is:
The total number of CMS Relative Weights for all of the cases divided by the total number of patients served.
Example: Commonwealth Hospital – Top 5 MS DRGs
The total CMS Relative Weight is 213.0332
The total number of patients served is 78
The Case Mix Index is 213.0332 / 78 = 2.7311
Part I Written Assignment
You are the HIM Director for PrimeCare Medical Center and you are charged with the task of analyzing your facility’s case mix and comparing your Case Mix Index with comparable facilities in your area. The top 5 procedures performed in your facility are listed below:
PrimeCare – Top 5 MS DRGs
- Calculate the Case Mix Index for the top 5 MS DRGs for your facility. Report all calculations to four places after the decimal point for the most accurate CMI.
- The Transplant Surgery Department has predicted a 20% increase in kidney cases for the next fiscal year and the Urology department has predicted a 10% decrease in major bladder procedures. Recalculate the CMI to account for these predictions. Report all calculations to four places behind the decimal point for the most accurate CMI.
- Prepare a short report (1 page) to the Finance Department that analyzes the impact of the projected changes in utilization practices. In your report include the new projected CMI. The purpose of the report would not be to give actual facts and figures just to identify areas that would be impacted by the projected changes.
Part II Written Assignment
Review the Case Mix Index figures in the table below.
Overall Case Mix Index FY 20xx
Facility Year 1 Year 2 Year 3
Hospital A 1.7694 1.9052 1.9689
Hospital B 1.5925 1.5554 1.7715
Hospital C 1.6443 1.7073 1.9003
Hospital D 1.5053 1.9471 1.8945
State Average 1.6667 1.7712 1.9085
a. Prepare a graphic representation that compares each of the hospital figures to the state average for each year.
b. Evaluate the data contained in the table. What types of conclusions can be drawn from this information about each hospital and the state average for each year? Prepare a short report (1 page) that evaluates the possible explanations as for why each facility’s overall CMIs were higher or lower that the state average for each year.