Measuring outcome.

In the context of health and illness, outcome is usually defined as the extent to which goals are achieved. It is necessary to understand: (i) the conceptual basis of the consequences of stroke; (ii) the context of measurement; and (iii) the calibre of the instruments available. In 1980, the World Health Organization provided an appropriate conceptual framework. The location, for example in-patient or out-patient, must be considered; as should the professional mix of the service; the time since onset and whether or not the setting is routine clinical practice or research. For the calibre of the measuring instruments psychometric studies report on reliability and validity. Other limitations and omissions in current measurement practice are being addressed through Item Response Theory. In clinical practice, current use of outcome measures is limited but it would seem that, by default at least, a core set of outcome measures is emerging.