Setting targets for CABG surgery in the north western region

A national target for coronary artery bypass graft (CABG) operations of 300 per million population was established by the Department of Health in 1987. Regional Health Authorities were required in 1993-1994 to achieve this target. The 1990-1991 Regional all-ages CABG rate was 239 per million population. The North Western Region planned to devolve the purchasing of certain services, including cardiac surgery, to districts in April 1993. Three districts had provider units within their boundaries. No means existed for estimating the appropriate operation rate, according to need, for district populations. A method was therefore devised for calculating guideline targets.

Based on the assumption that the ischaemic heart disease standardized mortality ratio (IHD SMR) is a valid proxy of the need for CABG operations and using a linear regression model, the existing district IHD SMRs and IHD hospitalization rates were used to derive guideline targets for districts, taking account of the need to raise the average operation rate for the Region to 300 per million population. Further targets using alternative Poisson regression model and weighting formulae were also derived.

The derived operation targets based on the linear regression model were lower than the existing operation rate in the three provider districts and in the biggest provider's two neighbours. In all other districts, except one, targets were higher than the existing number of operations. The two further analyses produced essentially similar results.

In the North Western Region wide variations in CABG operation rates existed. Access to CABG surgery in the North Western Region appears to depend on proximity to the provider districts. Operation rates should reflect need. This paper presents a method for deriving targets which take account of need.