Use of regression analysis to explain the variation in prescribing rates and costs between family practitioner...

There are proposals to set up prescribing budgets for family practitioner committees (now family health services authorities) and indicative prescribing amounts for practices. An intelligible model is therefore required for specifying budgetary allocations. Regression analyses were used to explain the variation in prescription rates and costs between the 98 family practitioner committees of England and Wales in 1987. Fifty one per cent of the variation in prescription rates and 44% of the variation in prescription costs per patient could be explained by variations in the age-sex structure of family practitioner committees. The standardized mortality ratio for all causes and patients in 1987, and the number of general practice principals per 1000 population in 1987, but not the Jarman under-privileged area score were found to improve the predictive power of the regression models significantly (P less than 0.01). The predictions of the model for the 10 family practitioner committees with the highest and lowest prescription rates or costs are reported and discussed. Potential improvements in models of prescribing behaviour may be thwarted by two problems. First, the paucity of readily available data on health care need at family practitioner committee and practice levels, and secondly, the increasing complexity in the statistical techniques required may render the procedure less intelligible, meaningful and negotiable in a contentious field.