Characteristics of GPs responding to an educational intervention to minimise inappropriate prescriptions: subgroup analyses of the Rx-PAD study

BACKGROUND: Interventions aimed at improving GPs’ prescribing practice usually apply a 'one size fits all' when analysing intervention effects. Few studies explore intervention effects by variables related to the GPs’ age, sex, specialist status, practice type (single-handed versus group), practice setting (urban versus rural), and baseline performance regarding the target of an intervention. AIM: To explore the characteristics of the GPs responding to a comprehensive educational intervention. DESIGN & SETTING: A secondary analysis of a cluster, randomised educational intervention in Norwegian general practice. Pre-intervention data were captured from January 2005 to December 2005, and post-intervention data from June 2006 to June 2007. The intervention was carried out from January to June 2006. METHOD: Eighty continuing medical education (CME) groups, including 449 GPs aged 27–68 years, were randomly allocated to either an education intervention arm (41 groups, 250 GPs) or a control arm (39 groups, 199 GPs). The primary outcome was GPs' change in potentially inappropriate prescriptions (PIPs) per 100 prescriptions issued to patients aged ≥70 years. The interaction between intervention outcome and variables related to the GPs and their practices were tested. RESULTS: Improvements in prescribing were highest among GPs aged 57–68 years (incidence rate ratio [IRR] = 0.77 [95% confidence interval {CI} = 0.73 to 0.81]), those who were specialists (IRR = 0.80 [95% CI = 0.78 to 0.82]), and those who worked in single-handed practices (IRR = 0.75 [95% CI = 0.68 to 0.83]), among GPs with 2.4 to 2.9 PIPs per 100 prescriptions at baseline (IRR = 0.74 [95% CI = 0.70 to 0.78]), and GPs with ≥15 prescriptions per patient per year at baseline (IRR = 0.77 [95% CI = 0.73 to 0.80]). CONCLUSION: The GPs with the lowest adherence to recommended practice at baseline improved their practice most.