Evaluation of endothelial activation and stress index (EASIX) formulae in patients with compound heterozygosity for hb s and β-thalassemia: Correlation with specific proteins of disease activity

Abstract

Abstract Background: Activation of vascular endothelium, the inner lining of blood vessels, has been previously reported in sickle cell disease (SCD) and has been attributed to several factors. This activation is a key factor in the development of vaso-occlusive crises and other complications in patients with SCD. Endothelial activation leads to increased adhesion of red blood cells and leukocytes, which can obstruct blood flow and cause tissue damage. Furthermore, endothelial activation in SCD contributes to the development of a chronic low-grade inflammatory state, which further exacerbates the disease process. Endothelial Activation and Stress Index (EASIX) and other modified EASIX-based formulae are indirectly calculated biomarkers that predict survival and other outcomes in various diseases, particularly those involving endothelial dysfunction. EASIX has been shown to be a valuable tool in predicting outcomes in several clinical entities, such as graft-versus-host disease (GVHD) after allogeneic stem cell transplantation, chimeric antigen receptor-T (CAR-T) cell therapies, sepsis, liver disease, COVID-19, and recently, cardiovascular diseases, including coronary artery disease, atrial fibrillation, and chronic heart failure. In this context, we aim to validate EASIX formulae in patients with SCD and correlate with specific markers of endothelial dysfunction, hemolysis, cardio-renal complications, as well as with other disease features. Patients and Methods: Data were collected and analyzed from 90 Caucasian adult patients with HbS/βthal at steady phase of disease. We calculated 3 EASIX-based formulae: EASIX [lactate dehydrogenase [(LDH; U/L) x Creatinine (mg/dl)/Platelets (PLTs; × 109 cells/L)], modified-EASIX (m-EASIX) [LDH; (U/L) x C-Reactive Protein (CRP; mg/dl)/Platelets (PLTs; × 109 cells/L)], as a marker of inflammation, and EASIX-Ferritin [LDH; (U/L) x Ferritin; (ng/ml) Platelets (PLTs; × 109 cells/L)], reflecting the iron burden, as we have described previously for other clinical conditions. Moreover, linearized correlation models and logarithmic transformations were used when appropriate. Levels of serum markers of cardio-renal and endothelial dysfunction, including high sensitivity troponin-T (hs-TnT), growth differentiation factor-15 (GDF-15), soluble urokinase-type plasminogen activator receptor (suPAR),von Willebrand factor antigen (vWF: Ag), a disintegrin and metalloproteinase with thrombospondin type 1 motif 13: antigen (ADAMTS-13: Ag), and P-selectin, of thrombo-inflammation, such as d-dimers, and of hemolysis and erythropoiesis, such as hepcidin-25 and placental growth factor (PlGF), were measured from samples obtained at the same time point. Additionally, bone marrow Activity (BMA), treatment with hydroxycarbamide, spleen size, number of VOC pain crises during the last year, and mean pulmonary arterial pressure(MPAP) were reported. Results: The findings of the study are presented as the best EASIX equation. We found that EASIX-Ferritin values correlated significantly with hs-TnT (r=0.261, p=0.014), GDF-15 (r=0.371, p<0.001), suPAR (r=0.448, p<0.001), vWF: Ag levels (r=0.346, p<0.001), and ADAMTS-13: Ag/vWF: Ag ratio (r=-0.324, p<0.01), while EASIX values correlated with P-selectin levels (r=-0.511, p<0.001). Moreover, EASIX-Ferritin values correlated significantly with D-dimer levels (r=0.318, p=0.003), PlGF (r=0.341, p=0.001), and hepcidin-25 levels (r=0.419, p<0.001), and m-EASIX values with BMA (r=0.290, p=0.005). Regarding EASIX score, it was found to be independent of hydroxycarbamide treatment and MPAP values, and associated with spleen size (r=0.342, p=0.015) and number of VOC during last year (p-trend=0.055). Conclusions: To the best of our knowledge, this is the first study to evaluate the potential significance of EASIX formulae in SCD. Regarding our findings, the EASIX-Ferritin-based formula seems to better reflect both the endothelial dysfunction and the hemolytic component of the disease in Caucasian patients with HbS/βthal. Further studies are essential on the role of EASIX formulae to fully elucidate their clinical significance and prognostic utility in patients with SCD, especially of different ethnic origins.