Elipsis: A Longitudinal Study of Electronic Patient-Reported Outcomes, Actigraphy and Biomarkers to Identify and Assess at-Home Vaso-Occlusive Crises in Adults and Adolescents with Sickle Cell Disease

Clinical trials in sickle cell disease (SCD) continue to have challenges achieving clinical endpoints. Most SCD clinical trials have focused on painful vaso-occlusive crisis (VOC) episodes because they are prevalent, debilitating and often lead to medical contact. However with VOC as a clinical endpoint: there are no objective, quantifiable biomarkers of pain; pain may not be specific to VOC; the threshold for medical contact varies between patients; VOCs occurring at home without medical contact are not captured; other components of VOC (e.g., fatigue, functioning) are poorly assessed. We therefore undertook the present non-interventional, longitudinal study to test novel tools for the identification of VOCs occurring in SCD patients with varying degrees of medical contact.

During 6 months of evaluation, longitudinal measures of pain, fatigue, function, activity (by actigraphy), clinical laboratory and biomarker samples from SCD patients (+/- hydroxyurea therapy) in steady state to VOC were studied. A novel electronic patient-reported outcome tool (ePRO) enabled patients to self-report daily pain, fatigue, function, and medication use. It was also used to report VOC in real time, triggering an alert to a mobile phlebotomy team. Blood collections were taken within 24 and 48 hours of self-reported VOC onset (either at home, emergency department [ED], or hospital). Follow-up blood samples were collected 2 days after resolution of the VOC. Baseline blood samples were drawn at home every 3 weeks during stable, non-VOC periods. Biomarker assays included leukocyte-platelet aggregates and circulating microparticles measured by flow cytometry, cell adhesion in microfluidic flow-based assays to immobilized vascular cell adhesion molecule or P-selectin, and a panel of soluble adhesion molecules, cytokines, inflammatory mediators and coagulation factors. Patients wore a Phillips Actiwatch Spectrum™ actigraphy device to track sleep and activity. Patient-reported outcomes, activity, and biomarkers on non-VOC days were compared to those on VOC days using a mixed model approach and results are reported as means with 95% confidence intervals (95%CI).

In this study 27 of 35 patients experienced a total of 286 days with VOC >4 hr (VOC days), of which only 58 days (20%) resulted in healthcare utilization such as contacting provider, visiting ED and/or hospitalization. VOC days had significantly higher pain scores (scale: 0-10) with worst pain score increased by 4.5 (95% CI 4.3-4.7) compared to non-VOC days. VOCs requiring medical contact had significantly higher worst pain scores compared to at-home VOCs. Similar changes observed with reported least, average and pain right now. VOC days had significantly higher fatigue scores by 2.3 (95% CI 2.1-2.5) points (scale: 0-10). However, fatigue scores during at-home VOCs were not different from VOCs requiring medical contact.

VOC days were associated with significantly decreased functional scores (physical, social, self-care and role activity), with significantly greater decreases during VOCs requiring medical contact compared to at-home VOCs. Different activity profiles were identified for non-VOC, at-home VOC and medical contact VOC days by actigraphy monitoring. At-home VOC days exhibited increased (34%, 95% CI 9%-64%) daytime resting compared to non-VOC days.

Medical contact VOCs had decreased average and peak activity, and increased daytime resting compared to non-VOC days. A sleep fragmentation index trended up for both at-home (16%) and medical contact VOC days (18%). Significant changes during VOC days were observed in a subset of clinical laboratory and biomarker measures. Examples include: C-reactive protein (54% increase) and nucleated RBC (34% increase) in the clinical laboratory panel; monocyte-platelet aggregates (25% increase) and neutrophil-platelet aggregates (35% increase) in the biomarker panel.

This innovative at-home study design demonstrates the feasibility of monitoring out of hospital pain and use of patient-reported VOC day as a potential endpoint for clinical trials. Electronic patient-reported outcomes, actigraphy and clinical laboratory and biomarkers may enable improved identification and assessment of at-home VOCs for further clinical studies.