Explaining variations in prescribing costs: results from a comparison of nursing home patients with matched pairs living in the community

Objectives: To examine and explain variations in prescribing costs associat ed with nursing home patients and patients matched by age and sex living in the community. Design: A la-month case control study. Subjects: All nursing home residents over 65-years-old registered with nine general practices and patients matc hed with them for age and sex living in the community. Method: Multivariate regression analysis of variations in monthly GP prescr ibing costs. Results: Multivariate regression models explaining cost variations in terms of the GP practice delivering care and patients' age and sex had little ex planatory power (R(2) = 0.07 for nursing home patients, R(2) = 0.03 for mat ched pairs). A fuller model for nursing home patients only, incorporating t he patients Barthel score and initial diagnosis as additional explanatory v ariables, added little to the explanatory power of the model (R(2) = 0.16). Conclusion: The ability of the multivariate models used here to explain var iations in prescribing costs among a group of elderly patients is poor. Adj usting weighted capitation formulae With respect to older patients to take account of such information or referring to it in negotiations on prescribi ng budgets would not appear to be warranted.