Regionalized delivery and variable utilization of coronary artery bypass grafting in Ontario from 1981 to 1991

To analyse the geographic variation in the rates of coronary artery bypass grafting (CABG) between 1981 and 1991.

Retrospective study of discharge abstracts (from the provincial hospital discharge database) for odd fiscal years.

Ontario.

All Ontario residents undergoing CABG between 1981 and 1991.

Age- and sex-standardized median, maximum and minimum (plus 25th and 75th percentile) rates of CABG per 100,000 population aged 20 years and over, as well as interregional variation.

The median rate of CABG rose from 46.2 to 72.7 per 100,000 adults between 1981 and 1991. The minimum rate varied from 1.9 to 12.4 per 100,000 and the maximum rate from 110.4 to 172.1 per 100,000 during the study period. Variations in the area-specific rates were significant in all years (p < 0.0001, based on the likelihood ratio chi 2 test after adjustment for age and sex). None of the four summary statistical measures showed any obvious diminution between 1981 and 1989, nor was there a change in the utilization pattern during the waiting-list crisis years of 1987 and 1989. However, the summary measures did reach their lowest level in 1991. The relative consistency of local practice patterns was tested by means of ranking area-specific rates and comparing the rankings for different years. Correlation coefficients varied from 0.50 to 0.82 (p < 0.0001); the correlation coefficient for 1991 on 1981 was 0.61 (p < 0.0001).

Consistent and marked variations in the use of CABG existed across the counties of Ontario from 1981 to 1991. Despite a major expansion in provincial caseload capacity and planned regionalization of CABG as a surgical service, incremental resources were apparently not allocated in a manner that reduced interregional discrepancies.