The practicality and validity of using outcomes to indicate the quality of stroke care

Routinely collected outcomes (case fatality by 30 days and discharge home by 56 days) have been used to indicate the quality of hospital stroke services in Scotland since 1994. However, the validity of these data is in doubt. In particular, it is difficult to know whether differences in outcome are due to differences in the quality of care or to inadequate adjustment for casemix, biased measurement or the play of chance. Also, because the majority of patients survive their stroke, the relevance and sensitivity of the indicators is limited by the failure to report functional outcome.It would be useful, therefore, to investigate whether a substantially improved system (one which adjusts comparisons of outcome for important differences in casemix and which measures functional outcome at a defined time after admission) would be routinely feasible and provide valid measurements of the quality of stroke care.We attempted to address these questions in the context of a study of 2724 patients with an acute stroke admitted to five Scottish hospitals between 1995 and 1997. We identified patients using routine hospital discharge information and then identified cases of acute stroke and data describing casemix and the process of care from the medical record. We collected case fatality by linkage to death certificate data and functional outcome and institutionalisation by postal survey at six months. We adjusted comparisons of outcome for casemix using a set of simple, externally validated logistic regression models.The study shows that a considerably improved routine system for measuring outcome after stroke is a realistic possibility. Specifically, it suggests that the proposed system for identifying hospital cohorts and collecting casemix data would be reasonably accurate and that the proposed system for measuring functional outcome, although compromised by non-response, would not be seriously biased. Nonetheless, whether these improvements would result in valid measurements of the quality of stroke care remains uncertain. At best, it appears that a system reporting case fatality and death or dependency at six months might be sensitive to moderately large differences in the quality of care. However, there may be alternative explanations for this finding and the system would certainly fail to identify opportunities to improve care at the majority of hospitals. The collection of data describing simple but important aspects of the process of care in addition to outcome might be preferable and should be investigated