Increasing the utilisation of hydroxychloroquine blood level testing in lupus: a quality improvement project.

Abstract

Objective: Hydroxychloroquine (HCQ) is a cornerstone therapy for SLE, reducing flares, organ damage and mortality. However, weight-based dosing yields highly variable drug exposure, which can result in suboptimal treatment. Measuring HCQ blood levels provides an objective tool to assess adherence and guide individualised dosing. Although available at our academic medical centre, this testing remains infrequently ordered in routine practice. We aimed to increase HCQ testing in patients with SLE through a structured quality improvement initiative and to characterise the clinical distribution of HCQ level results among tested patients.

Methods: We conducted a single-centre quality improvement project from August 2024 to November 2025 using a Plan-Do-Study-Act framework. Interventions included multidisciplinary education, development of institutional guidelines and implementation of an order set incorporating HCQ testing at prescribing. The primary outcome was the proportion of eligible patients with SLE with HCQ testing. As a secondary analysis, HCQ level results were categorised into four clinically meaningful ranges (severe non-adherence, subtherapeutic, therapeutic and supratherapeutic) based on published literature.

Results: Among nearly 1000 adult patients with SLE, HCQ testing increased from 4% to 15% (absolute increase of 11 percentage points; more than threefold relative). Provider adoption increased from 24% (8/33) to 73% (24/33) of rheumatologists. Among 170 tested patients, 79.4% had HCQ levels below the therapeutic range, including 14.7% with severe non-adherence (<200 ng/mL), approximately twice that in published cohorts.

Conclusions: This real-world quality improvement initiative demonstrates both the feasibility and clinical yield of integrating HCQ monitoring into routine SLE care. Beyond increasing test utilisation, monitoring revealed a substantial burden of HCQ exposure below the therapeutic range that would have remained invisible without systematic testing. The model is readily adaptable to other centres, particularly those serving populations facing access barriers.