This document details the methodology for the Non-Emergent Coronary Artery Bypass Graft (CABG) measure and should be reviewed along with the Non-Emergent Coronary Artery Bypass Graft (CABG) Measure Codes List file, which contains the medical codes used in constructing the measure.
Episode-based cost measures represent the cost to Medicare for the items and services provided to a patient during an episode of care (“episode”). In all supplemental documentation, “cost” generally means the standardized1 Medicare allowed amount,2 and claims data from Medicare Parts A and B are used to construct the episode-based cost measures.
The Non-Emergent CABG episode-based cost measure evaluates a clinician’s risk-adjusted cost to Medicare for patients who undergo a CABG procedure during the performance period. The measure score is the clinician’s risk-adjusted cost for the episode group averaged across all episodes attributed to the clinician. This procedural measure includes costs of services that are clinically related to the attributed clinician’s role in managing care during each episode from 30 days prior to the clinical event that opens, or “triggers,” the episode through 90 days after the trigger.
An average of approximately 100,000 Medicare patients underwent CABG surgery annually between 2000 and 2012.3 More than 13% of CABG patients are readmitted within 30 days,4 and each 30-day readmission for CABG resulted in additional costs up to $13,256.5 The Non-Emergent CABG episode-based cost measure was selected for development based on input from an expert clinician committee—the Cardiovascular Disease Management Clinical Subcommittee—because of its impact in terms of patient population and clinician coverage, and the opportunity for incentivizing cost-effective, high-quality clinical care in this clinical area.
Based on the initial recommendations from the Clinical Subcommittee, the subsequent measure-specific clinician expert workgroup provided extensive, detailed input on this measure.
The cost measure numerator is the sum of the ratio of observed to expected6 payment-standardized cost to Medicare for all Non-Emergent CABG episodes attributed to a clinician. This sum is then multiplied by the national average observed episode cost to generate a dollar figure.
The cost measure denominator is the total number of episodes from the Non-Emergent CABG episode group attributed to a clinician.
The Non-Emergent CABG cost measure uses the following data sources:
- Medicare Part A and B claims data from the Common Working File (CWF)
- Enrollment Data Base (EDB)
- Long Term Care Minimum Data Set (LTC MDS)7
Methodologically, the Non-Emergent CABG cost measure can be triggered based on claims data from: acute inpatient (IP) hospitals.
The cohort for this cost measure consists of patients who are Medicare beneficiaries enrolled in Medicare fee-for-service and who undergo a CABG procedure that triggers a Non-Emergent CABG episode.
The cohort for this cost measure is also further refined by the definition of the episode group and measure-specific exclusions (refer to Section 4).
1 Claim payments are standardized to account for differences in Medicare payments for the same service(s) across Medicare providers. Payment standardized costs remove the effect of differences in Medicare payment among health care providers that are the result of differences in regional health care provider expenses measured by hospital wage indexes and geographic price cost indexes (GPCIs) or other payment adjustments such as those for teaching hospitals. For more information, please refer to the “CMS Part A and Part B Price (Payment) Standardization - Basics" and “CMS Part A and Part B Price (Payment) Standardization - Detailed Methods” documents posted on the CMS Price (Payment) Standardization Overview page. (https://resdac.org/articles/cms-price-payment-standardization-overview).
2 Cost is defined by allowed amounts on Medicare claims data, which include both Medicare trust fund payments and any applicable beneficiary deductible and coinsurance amounts.
3 McNeely, Christian, Stephen Markwell, and Christina Vassileva. "Trends in Patient Characteristics and Outcomes of Coronary Artery Bypass Grafting in the 2000 to 2012 Medicare Population." The Annals Of Thoracic Surgery 102, no. 1 (2016): 132-38.
4 Li, Zhongmin, Ehrin J. Amstrong, Joseph P. Parker, Beate Danielsen, and Patrick S. Romano. "Hospital Variation in Readmission after Coronary Artery Bypass Surgery in California." Circulation: Cardiovascular Quality and Outcomes (2012).
5 Birkmeyer, J.D., Gust, C., Baser, O., Dimick, J.B., Sutherland, J.M., and Skinner J.S. "Medicare Payments for Common Inpatient Procedures: Implications for Episode-Based Payment Bundling." Health Serv Res 45, no. 6 Pt 1 (2010): 1783-95.
6 Expected costs refer to costs predicted by the risk adjustment model. For more information on expected costs and risk adjustment, please refer to Section 4.5.
7 For information on how LTC MDS data are used in risk adjustment, please refer to Section 4.5.