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Background SLE arthritis is difficult to evaluate because of the sometimes-evanescent nature of the symptoms and limitations of physical exams and imaging studies. Dynamic diffuse optical spectroscopy (dDOS) can be used to assess changes in light absorption through tissues during transient venous occlusion. The optical signal reflects changes in blood perfusion and has diagnostic value in rheumatoid arthritis. The current study explored the use of dDOS in SLE arthritis. Methods 12 SLE patients (ACR criteria) with active arthritis and 5 controls were evaluated. A dDOS sensor module was developed (figure 1a). Hemodynamic effects were obtained by inflating a BP cuff to 40 mmHg ×60 s. Light at 3 wavelengths (lambda=530, 655, 940 nm) was used to illuminate joints at 8 different points. Transmitted light intensities were measured with Si-photodetectors at 8 other positions (total 8×8×3=192 signal traces). Swollen, tender and healthy joints were examined by the same assessor. Results SLE patients and normal controls dDOS data were available for analysis from 66 and 24 proximal interphalangeal (PIP) joints, respectively (PIPs 2–4). Best results were obtained at 530 nm with cuff inflation at 40 mmHg. A representative measurement of 3 SLE arthritis and 3 normal joints is shown in figure 1b, highlighting differences in rise and plateau time. Given the pronounced effects at lambda=530 nm, we speculate that altered vessel physiology paired with already-increased blood pooling in the affected inflamed joints resulted in quicker increase in light absorption (rise time) that is maintained longer (plateau time) compared to normal joints. The AUC for dDOS was consistent with excellent discrimination, AUC=0.8639, sensitivity=76.19, specificity=88.57 (figure 1c). Conclusions dDOS can evaluate SLE arthritis with high sensitivity and specificity. Rise and plateau time of the optical traces correlate strongly with swollen and tender joint count. The advantages of dDOS are non-invasiveness, objectivity (eliminates inter-rater variability and operator dependency), low cost, and high speed of performance (~5 min per area of scanning) compared to US and MRI. dDOS has the potential to bring much-needed objectivity to the quantification of SLE arthritis. Funding Source(s): N/A

Background Hydroxychloroquine (HCQ) is a key component of therapy for Systemic Lupus Erythematosus (SLE). Medication non-adherence is reported in 40%–80% of lupus patients and results in increased morbidity, mortality, and health care utilization. HCQ levels are a sensitive and reliable method to assess medication adherence. Our study evaluated the feasibility of HCQ level measurement in a routine clinical setting and its association with disease activity in a predominantly Hispanic population. Methods SLE patients from the Columbia University Lupus cohort, treated with HCQ for ≥6 months and reporting medication-adherence were included. HCQ levels were measured by whole blood high performance liquid chromatography. Non-adherence was defined as HCQ level Results One-hundred and eight patients were enrolled (table 1); the mean age was 38 years, 91% were female, and 62% were Hispanic. The average SLEDAI-2K was 4.3 (0–20). Forty-one percent of patients had HCQ levels Conclusions HCQ levels Acknowledgements We acknowledge the patients who participated in this study.