Validity of stroke diagnosis on hospital discharge records in Saskatchewan, Canada: implications for stroke surveillance.

This study examines the validity of the diagnosis of stroke on hospital discharge records in Saskatchewan, Canada. In total, 1,494 records with a discharge diagnosis of 'stroke' or a 'stroke-related condition' were reviewed. The clinical algorithm of the 1980 USA National Survey of Stroke was considered the 'gold standard'. The positive predictive value of a primary diagnosis of stroke in the tertiary-care hospitals was about 90%. In community hospitals the majority of stroke cases were coded as ICD9 436 in which the positive predictive value was 78%. The variation between regions would limit the use of hospital discharge data for stroke surveillance.