Abstract
Sickle cell disease (SCD) is characterized by frequent and unpredictable vaso-occlusive crises (VOCs). Sickle erythrocytes (SSRBCs) contribute to VOCs by participating in a series of adhesive events with blood cells and the vascular endothelium. Adhesion assays have been used to evaluate the relationship between SSRBC adhesion and SCD severity. We developed a standardized, clinical flow adhesion assay of whole blood to vascular cell adhesion molecule (FA-WB-VCAM). The objective of this study was to assess the variability and clinical predictive value of FA-WB-VCAM in a six-month longitudinal, observational study (ELIPSIS) in SCD subjects during at-home, steady-state and self-reported VOCs, and following VOC resolution. We observed a strong relationship between FA-WB-VCAM and SCD severity. Adhesion indices were significantly lower in SCD subjects on hydroxycarbamide and increased during VOCs; at-home VOCs had significantly higher FA-WB-VCAM than steady-state and contact VOCs. SCD subjects with a high frequency of self-reported VOCs had a pro-adhesive phenotype at steady state and were stratified into a high-adhesive phenotype cohort; two years prospectively we observed a higher frequency of VOCs in the high-adhesion cohort. This study supports stratifying SCD subjects based on steady-state FA-WB-VCAM and suggests that FA-WB-VCAM may be a plausible surrogate end-point for SCD severity.