Introduction
This document details the methodology for the Acute Kidney Injury Requiring New Inpatient Dialysis measure and should be reviewed along with the Acute Kidney Injury Requiring New Inpatient Dialysis Measure Codes List file, which contains the medical codes used in constructing the measure.
Measure Description
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 Acute Kidney Injury Requiring New Inpatient Dialysis episode-based cost measure evaluates a clinician’s risk-adjusted cost to Medicare for beneficiaries who receive their first inpatient dialysis service for acute kidney injury during the performance period. The cost 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 the clinical event that opens, or “triggers,” the episode through 30 days after the trigger.
Measure Rationale
The annual expenditure of hospital-based AKI exceeds $10 billion, and each year there is approximately 600,000 cases of AKI.3,4 In 2015, 4.3 percent of Medicare beneficiaries experienced a hospitalization complicated by AKI.5 More specifically, over a nine-year span, over 1.09 million hospitalizations involved AKI requiring dialysis (AKI-D).6 Spending for hospitalizations with AKI-D showed an increase of $42,077 in hospitalization costs and an increase in length of stay by 11.5 days.7 The Acute Kidney Injury Requiring New Inpatient Dialysis episode-based cost measure was recommended for development by an expert clinician committee—the Renal Disease Management Clinical Subcommittee—because of its high impact in terms of patient population and Medicare spending, and the opportunity for incentivizing cost-effective, high-quality clinical care in this area. Based on the initial recommendations from the Clinical Subcommittee, the subsequent measure-specific workgroup provided extensive, detailed input on this measure.
Measure Numerator
The cost measure numerator is the sum of the ratio of observed to expected8 paymentstandardized cost to Medicare for all Acute Kidney Injury Requiring New Inpatient Dialysis episodes attributed to a clinician. This sum is then multiplied by the national average observed episode cost to generate a dollar figure.
Measure Denominator
The cost measure denominator is the total number of episodes from the Acute Kidney Injury Requiring New Inpatient Dialysis episode group attributed to a clinician.
Data Sources
The Acute Kidney Injury Requiring New Inpatient Dialysis cost measure uses the following data sources:
- Medicare Parts A and B claims data from the Common Working File (CWF)
- Enrollment Data Base (EDB)
- Long Term Care Minimum Data Set (LTC MDS) 9
Care Settings
Methodologically, the Acute Kidney Injury Requiring New Inpatient Dialysis cost measure can be triggered based on claims data from the following settings: acute inpatient (IP) hospitals
Cohort
The cohort for this cost measure consists of patients who are Medicare beneficiaries enrolled in Medicare fee-for-service and who receive their first inpatient dialysis service for acute kidney injury that triggers an Acute Kidney Injury Requiring New Inpatient Dialysis episode.
The cohort for this cost measure is also further refined by the definition of the episode group and measure-specific exclusions (see Appendix A).
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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 Price (Payment) Standardization - Basics" and “CMS Price (Payment) Standardization - Detailed Methods” documents posted on the Payment Standardization QualityNet webpage. (https://www.qualitynet.org/inpatient/measures/payment-standardization).
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. Claims data from Medicare Parts A and B are used to construct the episode-based cost measures
3 - Lysak, Nicholas, Azra Bihorac, and Charles Hobson. “Mortality and Cost of Acute and Chronic Kidney Disease after Cardiac Surgery.” Current Opinion in Anesthesiology, vol. 30, no. 1, 2017, pp. 113-117.
4 - Chawla, Lakhmir S, Richard L Amdur, Susan Amodeo, Paul L Kimmel, and Carlos E Palant. “The Severity of Acute Kidney Injury Predicts Progression to Chronic Kidney Disease.” Kidney International, vol. 79, no. 12, 2011, pp. 1361-1369.
5 - United States Renal Data System. 2017 USRDS annual data report: Epidemiology of kidney disease in the United States. National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 2017.
6 - Hsu, Raymond K, Charles E McCulloch, R Adams Dudley, Lowell J Lo, and Chi-yuan Hsu. “Temporal Changes in incidence of Dialysis-Requiring AKI.” Journal of the American Society of Nephrology, vol. 24, no. 1, 2012, pp. 37-42.
7 - Silver, Samuel A, Jin Long, Yuanchao Zheng, and Glenn M Chertow. "Cost of Acute Kidney Injury in Hospitalized Patients." Journal of Hospital Medicine, vol. 12, no. 2, 2017, pp. 70-76.
8 - Expected costs refer to costs predicted by the risk adjustment model. For more information on expected costs and risk adjustment, please refer to Section A.5.
9 - For information on how LTC MDS data are used in risk adjustment, please refer to Section A.5.