Trends and variations in the use of vascular surgery in Ontario

Objective — To measure changes over time in overall surgical rates and geographic rate variations for three major vascular procedures (abdominal aortic aneurysm repairs, peripheral vascular disease procedures and carotid endarterectomies).

Background — There is little research literature on population-based usage profiles of vascular procedures. The three procedures profiled were all subject to marked shifts in evidence or surgical opinions, raising the issue of the interplay between temporal trends and geographic variations in their use.

Methods — Based on Ontario's hospital discharge abstracts and census data, population-based usage rates were calculated by site of patient residence from 1981 to 1991. Extent of rate variation was summarized with the coefficient of variation, systematic component of variation and the adjusted-likelihood ratio chi2. Spearman rank correlations were also calculated to assess stability of county rankings for each procedure.

Results — The overall rates of peripheral vascular procedures and repair for abdominal aortic aneurysms fell 24% and increased 42% respectively. The overall rate of carotid endarterectomies dropped from 46/100,000 in 1981 to 20/100,000 in 1989, but by 1991 had increased to 37/100,000. Through the decade measures of variation fell minimally for all three procedures.

Conclusion — Overall use of vascular procedures shifted in apparent response to new research evidence and technologies. Despite marked changes in surgical rates, the extent of geographic variation was stable, suggesting that differing factors influence overall surgical rates and geographic rate variations. Audit at the local level using primary clinical data is needed to understand why disparities in use persist.