The standardized prescribing ratio--a new method for comparing prescribing between GPs, controlling for patient age and sex.

Objectives: To develop a method for comparing the proportion of patients on any drug or group of drugs for individual GP patient panels in Ireland, taking account of the age and sex structure of the panel.

Design: Calculations based on prescribing data for the fourth-quarter of 1995 supplied by the Irish General Medical Services Payments Board for the Eastern Health Board area.Setting-Five hundred and fifty Irish general practices serving 355,000 persons entitled to free medical care under the General Medical Services Scheme in the Eastern Health Board area (28% of the population).

Main Outcome Measures: Weightings for number of persons prescribed each of four drug groups, and all drugs combined, for 22 age/sex groupings, leading to a single age/sex adjusted prescribing index-the standardized prescribing ratio (SPR) for each GPs practice population.

Results: The SPRs showed a large amount of variation from the average figure of 100 for practices of 1000 or more patients for all drugs and for each of the four drug groups studied: all drugs 54-125, antibiotics 52-165, H(2) antagonists/proton pump inhibitors 38-197, antidepressants 13-213 and thyroxine 33-175. Practices with above average SPRs for all drugs, antibiotics and H(2) antagonists/proton pump inhibitors were significantly larger than those with below-average SPRs. Practices with below average SPRs for thyroxine were significantly larger than those with above-average SPRs.

Conclusions: The SPR provides a useful age/sex adjusted method of comparing prescribing between GPs and it can be applied to any drug or group of drugs.