Healthcare Utilization and Cost of Care Analysis of Patients with Sickle Cell Disease with High Vs. Low Biomarkers: A Retrospective Chart Review

Abstract

Sickle cell disease (SCD) is a red blood cell (RBC) disorder that is associated with frequent and unpredictable vaso-occlusive episodes (VOEs) including pulmonary hypertension, acute chest syndrome, chronic anemia, priapism, splenic and renal dysfunction, and stoke. The total cost to manage a SCD patient with a life expectancy of 64 years is between $1.3-$2.1M. Within the United States alone, up to 67% of adults have ≥3 VOEs per yearthat accounts for most of the healthcare utilization, including 78% of emergency room (ER) visits and 95% of hospitalizations. Despite the same single gene mutation of beta-globin, the frequency of VOEs amongst patients is highly variable. The pathophysiology of VOEs involves a complex interplay between circulating blood cells and elevated plasma factors that promote abnormal interactions to the vascular endothelium. Nearly a half century ago studies demonstrated RBC adhesion strongly correlates with disease severity however only recently standardized testing has become available to assess adhesion clinically. More specifically, we developed a suite of RBC health biomarkers and deployed our flow adhesion bioassays in our landmark, observational study (ELIPSIS). We established that flow adhesion of whole blood to vascular cell adhesion molecule-1 (FA -WB-VCAM) at baseline stratified SCD patients with severe disease phenotypes and validated the clinical predictive value of FA-WB-VCAM two years post-ELIPSIS. The objective of this study was to determine whether baseline FA-WB-VCAM biomarker levels could predict patients more likely to receive direct healthcare contact (ER visits/hospital admissions) to manage SCD complications. This study was a retrospective assessment of clinical FA-WB-VCAM in individuals with SCD during steady state between January 2020 through March 2023. Flow adhesion assays were performed using pulsatile, shear flow (1.67Hz, 1.0 dyne/cm 2). SCD patients that received at least 3 steady state FA-WB-VCAM biomarker evaluations within 1-year were included in this analysis. Clinical site received an IRB waiver to obtain patient-reported ER visits and hospitalizations during relevant time periods. We calculated a composite adhesion index by averaging baseline FA-WB-VCAM biomarker evaluations and established SCD disease severity by quantifying the number of ER visits and hospital admissions one year after the most recent FA-WB-VCAM biomarker evaluation. The non-parametric Wilcoxon matched pairs signed rank test was used to test the statistical differences between groups. Data are presented as mean ± standard error of mean. A p-value < 0.05 was considered statistically significant. Out of a total of 3939 clinical tests performed, 366 samples were obtained for “baseline” indications. Of these, only 28 samples were analyzed from 9 unique patients who met the study criteria described above. The average flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM) in SCD patients with high adhesion phenotypes (>400 cells/mm 2) was significantly higher than the low/moderate SCD cohort (mean high=603±78 cells/mm 2, mean low/moderate=343±28 cells/mm 2, p=0.02). More important, the high adhesion cohort had more ER visits (11 vs. 5) and hospitalizations (24 vs 9) and significantly higher healthcare costs ($35,871 vs. $13,563). This is the first healthcare cost analysis assessing the relationship between SCD patients stratified by their adhesive phenotype using the standardized, clinical adhesion biomarker FA-WB-VCAM, and healthcare utilization. The previous ELIPSIS study established that baseline FA-WB-VCAM stratifies patients based on their risk of developing self-reported VOCs during a 6-month longitudinal observation period and their risk of higher clinical disease severity in a 2-year follow-up study. Consistent with this data, the current study demonstrated that a cohort of SCD patients with elevated baseline adhesion phenotypes based on FA-WB-VCAM had a greater utilization of healthcare resources (ER visits and hospitalizations) and had a higher cost of care during the retrospective observation period. These data suggest that RBC health as indicated by “baseline” FA-WB-VCAM levels may predict lower health care utilization and costs, and that this biomarker may be a plausible surrogate endpoint to assess the pharmaco-economic impact of SCD-modifying therapies.