Objective: To assess the reliability and concurrent validity of the Medication Adherence Self-report Inventory (MASRI) when used in systemic lupus erythematosus (SLE), to investigate the predictive validity of the MASRI using pharmacy refill information as the criterion standard, and to propose a sensible approach to the screening for nonadherence in a clinical setting.
Methods: Adherence to 2 medications (hydroxychloroquine and prednisone) was measured in 55 patients using the MASRI, pill counts, and physician ratings (MD scale). Adherence based on pharmacy refill information served as a criterion standard with nonadherence defined as adherence rates <80%. To determine test-rest reliability of the MASRI, 20 patients completed the measure twice within a 2-week period.
Results: Using pharmacy information, 39% of the patients were nonadherent to prednisone and 51% to hydroxychloroquine. The MASRI had acceptable internal consistency (Cronbach's alpha 0.7) and good reliability. Irrespective of the drug assessed, MASRI ratings were moderately correlated with patient adherence (pharmacy), supporting the concurrent validity of the MASRI. The combination of adherence estimation by MD scale rating at <85% and by MASRI at <90% was 87% sensitive and 86% specific for identifying patients who were nonadherent to prednisone. These cutoff values also appeared suitable for identifying nonadherence to hydroxychloroquine.
Conclusion: The MASRI is a reliable measure of adherence to medications in SLE. The measure has concurrent and predictive validity. When combined with the MD scale, the MASRI appears to be a useful screening tool for nonadherence in patients with SLE that could be suitable for clinical practice.