Comparing hospitals on stroke care: the need to account for stroke severity.

STROKE IS A LEADING CAUSE OF MORBIDITY AND MORtality in the United States and worldwide and is associated with enormous health care expenditures. Approximately 800 000 new or recurrent strokes occur annually in the United States, and of these, about 87% are ischemic cerebral infarctions. Since 1996, when the use of intravenous tissue plasminogen activator was approved by the US Food and Drug Administration (FDA) for the treatment of patients with acute ischemic stroke within 3 hours of symptom onset, there has been a sea change in the approach to identification and management of stroke patients to improve their outcomes. Parallel to these advances, there has been an equally important move toward a systems-based approach to stroke care. The very short time window needed for acute therapies to reverse brain injury has inspired several national and statewide initiatives to improve hospital care of the stroke patient. The Brain Attack Coalition criteria for primary stroke centers, first recommended in 2000 and revised in 2011, have formed the basis for Joint Commission certification for stroke center status. Additional certification for comprehensive stroke centers begins in July 2012. These efforts are rooted in a developing evidence base demonstrating that organized, systems-based care, informed by guidelines and quality assurance efforts, can improve outcomes. There is evidence, for example, that patients with acute stroke are more likely to survive, return home, and regain independence if treated in hospital units specializing in the care of patients with stroke. The restructuring of health insurance in the United States, with the focus on increasing efficiency, improving outcomes, and providing value to the public, has stimulated efforts to provide valid measures of health care quality. One such measure includes assessment and ranking of hospital performance in the care of commonly encountered and significant illnesses, of which stroke is a good example. Approaches to the measurement of such outcomes, however, are potentially fraught with biases and other complexities. Although the implications of such measures are substantial, both for the individual hospital and the health care system as a whole, targeted research about health care–related outcomes is a relatively new field and optimal analytic approaches are still being developed. In this issue of JAMA, Fonarow and colleagues evaluate the influence of including or excluding stroke severity in prognostic stroke outcome models in a large Medicare insurance database. The authors used data from almost 128 000 patients with ischemic stroke from 782 Get With The Guidelines–Stroke participating hospitals. For all patients included in the analysis, information on the severity of the stroke was available in the form of the National Institutes of Health Stroke Scale (NIHSS) score. The primary outcome was 30-day mortality, and prognostic models were evaluated for their overall model discrimination as well as for differences in rankings of the hospital performance when including or excluding information on stroke severity. The main prognostic model included information on age, sex, prior stroke or transient ischemic attack, and a large number of comorbid conditions and was compared with a model that additionally included information on stroke severity. All statistical measures of model performance showed that the model including stroke severity was superior, indicating that stroke severity substantially improved the prediction of 30-day mortality above and beyond other clinical predictors. Considered at the level of the individual patient, this result does not seem surprising: a patient who has a relatively more severe stroke is at increased risk of death. Moreover, when the prediction models were used to classify and rank hospitals based on 30-day mortality, the model including stroke severity demonstrated substantially more accurate classification and substantially changed hospital rankings. Of the 782 participating hospitals, the absolute change of the median hospital rank position was 79 places. More than half (58%) of hospitals first classified as having higher than expected mortality were reclassified to having the expected mortality rate after incorporating severity into