Adherence to hydroxychloroquine in patients with systemic lupus: Contrasting results and weak correlation between assessment tools

Abstract

Objectives: Hydroxychloroquine (HCQ) is an anchor drug in the treatment of systemic lupus erythematosus (SLE). Adherence to HCQ is key for efficacy. Inaccurate evaluation of adherence could lead to non-justified switch to more expensive or less tolerated drugs.

Methods: Severe non-adherence rate to HCQ was estimated in a sample of SLE patients during a routine visit using blood HCQ concentration<200μg/L. Adherence was assessesd by the Medication Adherence Self-Report Inventory (MASRI)<80/100, 8-item Morisky Medication Adherence Scale (MMAS-8) ≤6/8, Health Care Provider (HCP) visual analog scale (VAS)<80/100. Same procedures were to be repeated during a further routine visit 6 to 12 months later. We described agreement and correlations between tools and compared severely non-adherent patients and others on their characteristics.

Results: The study involved 158 patients (86.1% females) aged 42.2±12.6 years treated with HCQ for 9.6±6.9 years. Blood HCQ concentration (mean±standard deviation) was 1046±662μg/L at visit 1 and 855±577μg/L at visit 2. At visit 1, the non-adherence rate varied from 3.2% (blood HCQ level<200μg/L) to 7.7% (MASRI), 12.4% (HCP-VAS) or 32.5% (MMAS-8). 37.8% of patients met at least one of the definitions of non-adherence. Patients' characteristics including SLE activity, damage and quality of life were similar between severely non-adherent patients and others. Correlations between blood HCQ-concentration and self-questionnaires were weak (r<0.25) and agreement between methods was poor.

Conclusion: Blood HCQ concentration<200μg/L reveals severe non-adherence. Combining blood HCQ concentration with MASRI and MMAS-8 may help to better identify non-adherence in SLE. Agreement between methods was poor and correlations with HCQ level and SLE activity were weak.

Keywords: Systemic Lupus Hydroxychloroquine Adherence.