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

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.

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.

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.

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.