Regional comparisons of inpatient and outpatient patterns of cerebrovascular disease diagnosis in the province of Alberta.

The diagnosis of cerebrovascular disease (CBVD) from administrative data has been critically examined by epidemiologists in recent years. Much of the existing literature suggests that hospital discharge diagnoses based on ICD-9-CM codes are an unreliable source of information for determining a diagnosis of stroke, particularly when four- and five-digit codes are used. We examined how diagnoses for CBVD in hospital inpatient and outpatient facilities vary between rural and urban areas and among the 16 administrative health regions. Our analysis revealed differences in diagnostic patterns between the two sources of data, differences between rural and urban areas, and variation across most of the regions. Geographic variation in health service utilization, diagnostic practices, specialty of the physician making the diagnosis, and disease burden may explain our findings. Our results suggest that the diagnosis of patients attending rural facilities are either coded differently (and less precisely) than those of urban residents or are coded more precisely only after the patients attend urban facilities. Regional differences in coding practices show that any CBVD surveillance system based on administrative data requires a large-scale (in this case, province-wide) and person-oriented approach.