Predicting disability in stroke--a critical review of the literature

Research articles on the prognosis of stroke patients were analysed to identify studies that met sound methodological principles of prognostic research as well as to identify variables capable of predicting functional outcome (ADL) after stroke. Data sources comprised a computer-aided search of published prognostic studies and references to literature used in prognostic studies. Seventy-eight studies were tested for adherence to the following key methodological criteria: reliability and validity of measurement instruments used to assess dependent and independent variables; inclusion of an inception cohort; adequate and uniform end-point of observation; control for drop-outs during period of observation; statistical testing of presumed relationship between dependent and independent variables; sufficient sample size in relation to number of determinants; control for multicollinearity; specification of patient characteristics (i.e. age, type, recurrent stroke and localization of stroke); description of interfering treatment effects during the period of observation, and cross-validation of the prediction model in a second independent group of patients. Only three studies satisfied nine out 11 criteria and ten studies eight criteria for the determination of valid prognostic research. The results of these studies indicate that the following variables are valid predictors for functional recovery after stroke: age; previous stroke; urinary continence; consciousness at onset; disorientation in time and place; severity of paralysis; sitting balance; admission ADL score; level of social support and metabolic rate of glucose outside the infarct area in hypertensive patients. This study supports the general opinion that not only are differences in objectives and heterogeneity in stroke patients responsible for the lack of accuracy in predicting functional outcome, but also the methodological flaws in published prognostic research.