Background/Purpose: Hydroxychloroquine (HCQ) is known to reduce flares, improve disease activity and mortality in patients with systemic lupus erythematosus (SLE).¹ Nonadherence to HCQ is a noteworthy threat among patients with SLE, but can be objectively and reliably identified via whole blood concentration measurement.² Routine monitoring of HCQ blood levels identifies nonadherence and could improve long term outcomes in patients with SLE.³ Ordering patterns of HCQ whole blood levels are not well understood. Determining patterns of HCQ monitoring among providers and could identify an area for intervention to improve outcomes for patients with SLE.

Methods: This study is a retrospective review of patients ≥ 18 years old with SLE with active HCQ prescriptions who have had [HCQ] labs ordered or performed at YNHH system from January 2018-January 2023. The total number of HCQ orders, total number of HCQ results and HCQ levels with their respective dates of service were reviewed from subjects with a chart diagnosis of SLE. HCQ nonadherence was defined as ≤ 250 ng/mL.

Results:

• From 2018-2023, 7,394 adult patients had a chart diagnosis of SLE in the YNHH system.
• 47.84% of these patients were on active HCQ prescriptions within this timeframe.
• There were 281 available [HCQ] results with numerical values were available for review.
• 23.5% of all [HCQ] orders resulted in values ≤ 250 ng/mL with the majority (68.2%) being undetectable.
• 33.1% of unique patients with available [HCQ] results had at least 2 results.
• 68.7% of results were from 2023, 31.0% of results were from 2022, 0.3% of results were from 2021, with no results from 2018, 2019, or 2020.
• The average [HCQ] for patients with one result was 709.7 ng/mL with 15.0% of results ≤ 250 ng/mL, while the average [HCQ] for patients with multiple results was 642.3 ng/mL with 16.7% of results ≤ 250 ng/mL.
• For patients who had multiple [HCQ] results and a baseline [HCQ] ≤ 250 ng/mL, the results from the initial [HCQ] (M = 58.1, SD = 82.5) and the final [HCQ] (M = 286.9, SD = 324.0) demonstrate significantly higher final [HCQ] results, t(16) = 2.74, p = .007).

Conclusion:

• HCQ blood monitoring is increasing in frequency at Yale New Haven Hospital.
• A significant portion of patients were found to be nonadherent when HCQ blood monitoring was utilized.
• Repeated HCQ level monitoring resulted in an average increase of HCQ concentration.
• Providers should be educated in the utility of HCQ blood level monitoring.
• Limitations of the study include the retrospective nature, the difficulty in identifying early HCQ blood orders due to assignment of “miscellaneous” in the electronic medical record, and HCQ testing has only recently been studied and early questions relating to the operating characteristics of the assay resulted in poor early uptake.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/project-hope-hydroxychloroquine-adherence-project/