Background:~Statin therapy is known to improve clinical outcomes in patients with coronary artery disease (CAD), while being highly cost-effective. However, adherence to statin therapy in real world settings is suboptimal and represents a possible target to ameliorate secondary CAD disease prevention. Previous interventional studies on statin adherence showed inconsistent results and it is widely acknowledged that a tailored adherence improvement approach adapted to patient determinants is required. However, methodology to accurately detect and characterize non-adherent patients is challenging and constitutes an important obstacle to developing such interventions. Urine analysis with liquid chromatography/mass spectrometry (LC-MS) for detection of statin intake is a promising method for objective measurement of adherence as an adjunct to subjective adherence assessment using questionnaires, which has not been applied in CAD patients in Germany.~Objectives: In this pilot study (i) a feasibility testing of objective (LC-MS urine analysis) and subjective (questionnaire survey) measures of adherence to statin therapy will be performed, (ii) the prevalence of nonadherence in the target population will be determined , and (iii) instruments assessing possible factors associated with (non-)adherence (e.g. side effects, beliefs about medications, and disease-related knowledge) will be evaulated, in order to establish a methodological ground for further studies characterizing non-adherent patients.~Methods:~Outpatients with CAD treated in University Hospital Düsseldorf and receiving guideline-recommended atorvastatin or rosuvastatin on prescription will be included in the pilot study. Based on sample size calculation about 130 patients will be recruited. A biochemical method of objective urine measurement of statin intake by LC-MS will be combined with a preselected set of questionnaires on adherence behavior and associated factors. Clinical characteristics will be obtained from patient records. A sub-sample of the study population will be invited to participate in the interview for the evaluation of the questionnaire survey.~Outlook:~Based on the results of the pilot study, an adequately powered study to characterize non-adherent patients and identify patterns of non-adherence will be conducted. The results will be used for the development of a complex tailored intervention for non-adherent patients in Germany.
Feasibilty study of biochemical urine analysis of adherence to high intensity statin therapy in outpatients with coronary artery disease