616 Lower hydroxychloroquine blood levels are associated with higher Type 1 and 2 lupus activities

BackgroundHydroxychloroquine (HCQ) is a mainstay of the initial and long-term treatment of systemic lupus erythematosus (SLE). HCQ blood levels can reflect adherence to the medication and have been correlated with SLE outcomes. However, little is known about the relationship between HCQ levels and SLE disease activity according to the Type 1 & 2 SLE Model, in which Type 1 activity is thought to be mediated by inflammation, e.g., arthritis, rash, nephritis, and Type 2 manifestations have uncertain relationship to inflammation, e.g., fatigue, myalgias, mood disturbance, and cognitive dysfunction.MethodPatients meeting the 1997 American College of Rheumatology or 2012 Systemic Lupus International Collaborating Clinics classification criteria for SLE were recruited from an academic lupus clinic. Whole blood HCQ levels were measured in Exagen’s clinical laboratory using liquid chromatography coupled to mass spectrometry and were categorized as under-exposure (HCQ 1000 ng/ml). Type 1 SLE activity was measured by Type 1 Physician Global Assessment (PGA) and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Type 2 SLE activity measures included Type 2 PGA and patient-reported Polysymptomatic Distress (PSD) score (sum of widespread pain index and symptom severity score). Type 1 and 2 SLE Model classifications are defined in table 1. Self-reported adherence to HCQ was measured using the visual analog scale of the Medication Adherence Self-Report Inventory.We examined demographic and clinical differences among patients with different HCQ blood levels using the Chi-squared and Kruskal-Wallis tests. We also examined the distribution of HCQ levels across different types of lupus activities.ResultsThis cross-sectional analysis included 156 patients (median age 42, 91% female, 61% black, 43% married or cohabiting, 60% with annual household income ≤$50,000, and 47% with Medicaid/Medicare insurance). In this cohort, 32% were classified to have Minimal SLE (low Type 1 & 2 activity), 12% had active Type 1 with low Type 2 SLE activity, 24% had active Type 2 with low Type 1 SLE activity, and 32% had Mixed SLE (high Type 1 & 2 activity).Of the 127 patients who provided adherence data, 70% reported ≥90% adherence to the prescribed dose. HCQ whole blood levels were in the under-exposure range in 19%, subtherapeutic in 35%, and therapeutic in 46% of patients (table 2).No significan