Understanding adherence to official guidelines on statin prescribing in primary health care--a multi-level methodological approach.

Objective: The aim was to investigate the role that municipalities and out-patient health care centres (HCCs) have in understanding adherence to official guidelines on statin prescribing. Our hypothesis was that after guideline publication, adherence to recommended statin prescription would increase and variance among HCCs and municipalities would decrease. Since multi-level regression analysis (MLRA) is a relatively new methodology in pharmacoepidemiology, we also aimed to explore the application of MLRA in our investigation.

Methods: We obtained data from the Swedish Corporation of Pharmacies record of sales regarding all initial prescriptions of statins issued between April and December 2003. We applied multi-level analysis on 34,514 individual prescriptions (level 1) nested within 226 HCCs (level 2), which in turn were nested within 33 municipalities (level 3). Temporal trends and gender differences were investigated by means of random slope analysis. Variance was expressed using median odds ratio (MOR) and interval odds ratio.

Results: HCCs appeared to be more relevant than municipalities for understanding the physicians' propensity to prescribe a recommended statin (MOR(HCC) = 1.96 and MOR(Municipality) = 1.41). Overall prevalence of adherence was very low (about 20%). After publication of the guidelines, prescription of recommended statins increased, and variance among HCCs decreased but only during the first 4 months of the observation period.

Conclusion: The publication of official guidelines in the county of Scania exerted a positive influence on statin prescription but, at the end of the observation period, adherence was still low and practice variation high. These facts may reflect inefficient therapeutic traditions and suggest that more intensive interventions may be necessary to promote rational statin prescription.