Risk Adjustment of Ischemic Stroke Outcomes

Updated:Jan 29,2014
Risk Adjustment of Ischemic Stroke Outcomes for Comparing Hospital Performance: A Statement for Healthcare Professionals from the American Heart Association/American Stroke Association
Irene Katzan, John Spertus, Janet Prvu Bettger, Dawn M. Bravata, Mathew J. Reeves, Eric E. Smith: [Epub 1/23/14] STROKE
Stroke is the fourth leading cause of death and a leading cause of long-term disability in the United States. Measuring outcomes after stroke and using risk-adjusted models to predict the mortality, readmission rates, and functional status of ischemic stroke patients has important policy implications. This paper gives an overview of the science and statistical considerations for evaluating hospital outcomes after stroke, discusses the benefits and limitations of these outcome measures, and provides recommendations on the minimum list of variables to be included in these models.
Key Points:
  • The three outcome measures addressed are: 1) functional outcomes, 2) mortality, and 3) 30-day readmission.
  • The following factors should be included in all hospital-level risk-adjustment models: age, gender, stroke severity, comorbid conditions, vascular risk factors, and pre-stroke function.
  • Evidence shows that stroke severity is the most important factor as it relates to stroke outcome for stroke patients and to hospital level performance for 30-day stroke mortality.
  • Because a clear link between quality of hospital care and outcomes after stroke has not been well demonstrated, there is a need to define the relevant stroke outcomes to measure.
  • Risk adjustment models should include some way to measure stroke severity.
  • There is a wide variation in hospital ischemic stroke mortality that occurs despite adjustments for age, sex and comorbid conditions. In a study of Medicare ischemic stroke patients admitted to 625 hospitals participating in a quality improvement program, hospital 30-day risk-adjusted standardized mortality varied by more than 75 percent.
  • Better organized inpatient stroke care is associated with lower mortality, but it is not clear why. Short-term stroke mortality may be more reflective of patient/family preferences than the provision of evidence-based care, and hospitals that practice optimal shared decision-making could have higher mortality rates due to higher rates of appropriate use of palliative care.
  • The problem with using data from administrative data is that these are collected primarily for billing purposes and may not capture important clinical data known to be associated with outcomes. A significant challenge for risk adjustment of stroke outcomes with either administrative or clinical data is that measures of stroke severity, such as the National Institutes of Health Stroke Scale (NIHSS) are frequently missing. Critical issues in considering risk models for mortality after acute ischemic stroke are whether clinical assessment of stroke severity is necessary or feasible. This is important in light of CMS’ recent decision to publicly report stroke mortality using administrative data for risk adjustment that does not include a measure of stroke severity.
When using mortality as an evaluation of stroke care in the hospital, age, gender, stroke severity, comorbid conditions, and vascular risk factors should be included at a minimum. Inclusion of a stroke severity measure in risk adjustment models for 30-day outcome measures is recommended. More research is needed on using mortality as an indicator of hospital quality.
There should be some type of standardized model used at all hospitals caring for stroke patients, and the reliability and accuracy of a standardized model should be the same across all facilities.
Using a combination of outcome measures – stroke mortality, functional status after stroke, and hospital readmission rates – may provide the best overall evaluation of hospital care.
Because the link between quality of hospital care and outcomes has not been robustly demonstrated (as well as the use of case-mix adjusted outcomes), more research is needed to better identify methods and metrics to evaluate stroke outcomes.
Other Resources:
Target: Stroke Time Lost Is Brain Lost. Read more about this program.
Focus on Quality The more healthcare quality improves, the more patient outcomes do too.