Background: Sickle cell disease (SCD) is a multi-system, life-threatening disorder that leads to a wide spectrum of clinical complications. It is characterized by a complex thromboinflammatory state that affects all components of Virchow's triad. The interplay between inflammation and coagulation leads to microvascular thrombosis, which is at the core of several complications associated with the disease including episodes acute chest (ACS), and vaso-occlusive (pain) crisis (VOC). However, patients with SCD exhibit substantial variability in disease phenotype and severity, and genotype-based stratification cannot fully capture the complexity of disease phenotype in this population. Biomarker data to inform predictions of disease phenotype and burden in children with SCD are lacking.

Aim: To identify plasma markers of inflammation and endothelial damage predictive of the development ACS and VOC, and of recurrent (>1) hospital admissions for these complications.

Methods: Clinical data and plasma samples from a multicenter, prospective, inception cohort study with biobanking of children with SCD were analyzed. Children (<21 years old) with SCD of any genotype admitted (March 2023 – April 2025) with an acute episode of ACS or VOC were included. Plasma samples were collected at the time of acute presentation (enrollment), during the convalescent period (6 weeks – 3 months after admission) and at the time of readmission for ACS and/or VOC in those with >1 admission during follow up. Clinical data were collected prospectively including demographic data, prior history of SCD severity and therapies, signs and symptoms at the time of presentation, and treatment received for the acute event. Inflammatory cytokines and cell adhesion molecules were detected in plasma using custom ProcartaPlex panels, on a Luminex™ 200 instrument (Invitrogen, Waltham, MA). Descriptive statistics were used to summarize the data. Biomarkers predictive of ACS, VOC or recurrent admissions were evaluated via univariate logistic regression, using odds ratios (OR) and 95% confidence intervals (CI).

Results: A total of 43 children with SCD were included (ACS n= 22, VOC n=21). Mean age was 11.5 years, 35% were female, and most frequent SCD genotype was Hb-SS (72%). Children with ACS were younger compared to those with VOC (7.4 years vs. 12 years; p<0.001). They also had a higher frequency of Hb-SS/Sβ0thalassemia (81% vs. 71%), prior recurrent episodes of ACS (32% vs. 14%) and VOC (23% vs. 14%), and a higher frequency of asthma (41% vs. 29%), but these differences were not statistically significant. Children presenting with ACS had higher median plasma levels of C-X-C motif chemokine ligand 10 (CXCL10) at enrollment and readmission (8 ng/mL vs. 3.5 ng/mL, p=0.002; 6.7 ng/mL vs. 4.2 ng/mL, p=0.009, respectively), vascular endothelial growth factor A at enrollment (VEGFA; 45 ng/mL vs. 26 ng/mL, p=0.004) and vascular cell adhesion molecule-1 at readmission (VCAM-1; 324 ng/mL vs. 162 ng/mL, p=0.013) compared to those presenting with VOC. In logistic regression analysis, CXCL10 at enrollment remained independently associated with the development of ACS (OR= 1.13, 95%CI 1.01, 1.27; p=0.038).

Sixty-three percent (n=27) of children had a single admission, 33% (n=14) had 2-3 admissions and 5% (n=2) had >3 admissions during follow up. Children with >1 admission more frequently had SS/Sβ0thalassemia genotype (94% vs. 70%, p<0.001) and received chronic blood transfusions (44% vs. 17%, p=0.032) compared to those with a single admission. Compared to children with a single admission, children with >1 admission had higher median plasma levels of several biomarkers including E-selectin, P-selectin and interleukin-6 but these differences were not statistically significant.

Conclusions: In this analysis, we identified higher median plasma levels of CXCL10, VEGFA and VCAM-1 at the time of presentation with an acute episode of ACS compared to VOC in children with SCD. Elevated plasma CXCL10 was independently associated with the development of ACS in pediatric SCD. Mass spectrometry proteomics and functional coagulation assays are currently being conducted to further identify molecular markers predictive of SCD complications in children.

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2025
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