Therapeutic Hydroxychloroquine Blood Levels are Associated with Lower Lupus Hospitalizations and May Reduce Health Disparities in Lupus.

Abstract

Hydroxychloroquine (HCQ) nonadherence is associated with a 3-fold higher risk of lupus-related hospitalization. Monitoring HCQ blood levels could improve adherence and efficacy. Yet, HCQ level monitoring is not routinely done partially due to cost and coverage concerns. To establish HCQ level monitoring cost-effectiveness, we reported: 1) risk of acute care utilization by HCQ blood levels; 2) cost of HCQ monitoring vs. acute care visits. HCQ blood levels were measured during routine lupus visits. HCQ levels were categorized as: a) subtherapeutic (<750 ng/ml), b) therapeutic (750-1200 ng/ml), or c) supratherapeutic (>1200 ng/ml). All lupus-related acute care visits (ER visits/hospitalizations) after the index clinic visit until next follow-up were abstracted. In our primary analysis, we examined associations between HCQ levels and time to first acute care visit in all patients and subgroups with higher acute care utilization. A total of 39 lupus-related acute care visits were observed in 181 patients. Therapeutic HCQ blood levels were associated with 66% lower acute care utilization. In our cohort, two groups, people of Black race or Hispanic ethnicity and those with public insurance, faced 3-4x higher acute care utilization. Levels within 750-1200 ng/ml were associated with 95% lower acute care utilization in subgroups with higher acute care utilization. HCQ blood levels within 750-1200 ng/ml are associated with lower acute care utilization in all patients with lupus, including groups with higher acute care utilization. Future clinical trials should establish the causal association between HCQ level monitoring and acute care utilization in lupus.