30-day death and readmission measures
The 30-day death (mortality) measures are estimates of deaths from any cause within 30 days of a hospital admission, for patients hospitalized with one of several primary diagnoses, regardless of whether the patient dies while still in the hospital or after discharge. CMS chose to measure death within 30 days instead of inpatient deaths to use a more consistent measurement time window because length of hospital stay varies across patients and hospitals. Also, mortality over longer time periods (such as 90 days) may have less to do with the care received in the hospital and more to do with other complicating illnesses, patients’ own behavior, or care provided to patients after hospital discharge. Hospital Compare reports on the following 30-day mortality measures:
- 30-day death rate for heart attack (AMI) patients
- 30-day death rate for heart failure (HF) patients
- 30-day death rate for pneumonia patients
The 30-day readmission measures are estimates of unplanned readmission for any cause to any acute care hospital within 30 days of discharge. CMS chose to measure readmission within 30 days instead of over longer time periods (such as 90 days), because readmissions over longer periods may be impacted by factors outside hospitals’ control such as other complicating illnesses, patients’ own behavior, or care provided to patients after discharge. Hospital Compare reports the following 30-day readmission measures:
- 30-day readmission for heart attack (AMI) patients
- 30-day readmission for heart failure (HF) patients
- 30-day readmission for pneumonia patients
- 30-day readmission for hip/knee replacement patients
- 30-day hospital-wide all-cause rate of readmission (Note: This measure includes patients admitted for internal medicine, surgery/gynecology, cardiorespiratory, cardiovascular, and neurology services. It is not a composite measure.)
What patients are included
The 30-day mortality and readmission measures include hospitalizations for Medicare beneficiaries aged 65 or older who were enrolled in Original Medicare (traditional fee-for-service Medicare) for the entire 12 months prior to their hospital admission (and for readmissions, for 30 days after their original admission). The acute myocardial infarction (AMI), heart failure (HF), and pneumonia mortality and readmission measures also include patients aged 65 or older who were admitted to Veteran’s Health Administration (VA) hospitals. Beneficiaries enrolled in Medicare managed care plans are not included. Readmission measures do not include patients who transferred to another hospital, or who left the hospital against medical advice.
Where the information comes from
CMS calculates hospital-specific 30-day mortality and 30-day readmission rates using Medicare claims and eligibility information. The AMI, HF, and pneumonia mortality and readmission measures are also calculated using VA administrative information. Using administrative data makes it possible to calculate mortality and readmission rates without having to do medical chart reviews or requiring hospitals to report additional information to CMS. Research conducted during development of the AMI, HF, and pneumonia measures showed that models based on administrative information performed well in estimating hospital mortality rates compared to models that are based on information from medical chart reviews.
Calculation of the 30-day mortality and 30-day readmission measures adjusts for patient characteristics that may make death or readmission more likely, even if the hospital provided quality care—including the patient’s age, gender, past medical history, and other diseases or conditions (comorbidities) the patient had when they were admitted that are known to increase the patient’s risk of dying or readmission.
The statistical model used to calculate 30-day mortality and 30-day readmission measures also determines how precise the estimates are, and provides the upper and lower bounds (“interval estimates”) for each hospital’s risk-adjusted mortality and readmission rates. Interval estimates, which are like confidence intervals, describe the level of uncertainty around the estimated mortality and readmission rates.
Comparing individual hospital rates to the U.S. national rate
To assign hospitals to performance categories, the hospital’s interval estimate is compared to the U.S. national 30-day mortality rate and 30-day readmission rate. If the interval estimate includes and/or overlaps with the national observed mortality or readmission rate, the hospital’s performance is in the “No Different than U.S. National Rate” category. If the entire interval estimate is below the national observed mortality or readmission rate, then the hospital is performing “Better than U.S. National Rate.” If the entire interval estimate is above the national observed mortality or readmission rate, its performance is “Worse than U.S. National Rate.” Hospitals with fewer than 25 eligible cases are placed into a separate category that indicates that the hospital does not have enough cases to reliably tell how well the hospital is performing.
For more detail on how the 30-day mortality rates are calculated, please refer to QualityNet - Mortality Measures- Opens in a new windowGlobe icon. For other questions regarding 30-day mortality measures, please email firstname.lastname@example.org.
For more detail on how the 30-day readmission rates are calculated, please refer to QualityNet - Readmission Measures- Opens in a new window Globe icon. For other questions regarding 30-day readmission measures, please email email@example.com.