Soluble CD163 in Young Sickle Cell Disease Patients and Their Trait Siblings: a Biomarker for Pulmonary Hypertension and Vaso-occlusive Complications

CD163 is expressed on cells of monocyte-macrophage lineage and is the main hemoglobin-haptoglobin receptor. Inflammation and monocyte activation are predisposing factors to vaso-occlusion and pulmonary hypertension, which are serious complications in sickle cell disease (SCD). Siblings of SCD patients may have the same pathophysiology without displaying symptoms. We assessed soluble CD163 (sCD163) levels in 60 children with SCD and 30 sickle cell trait (SCT) siblings compared with 30 healthy controls as a potential marker for disease severity and treatment response. Patients were studied stressing on the presence of pulmonary hypertension by Dopplar-Echocardiography, sickling crisis, transfusion requirements, hydroxyurea response, hematological profile, high sensitivity C-reactive protein (hs-CRP) and serum sCD163. sCD163 was significantly elevated in SCD patients and SCT siblings compared with controls and the highest levels were in untreated SCD patients (P < 0.001). sCD163 was higher in patients with pulmonary hypertension, acute chest syndrome or stroke as well as in patients who developed sickling crisis during the study period (P < 0.05). Hydroxyurea-treated patients had lower sCD163 compared with untreated patients (P < 0.001). sCD163 was positively correlated to leukocyte count, HbS, hs-CRP, pulmonary artery pressure and tricuspid regurgitant velocity whereas inversely correlated to hemoglobin and HbF levels. The cut-off value of sCD163 at 1400 ng/ml could be considered a predictor for vaso-occlusive crisis in SCD with a sensitivity of 92.3% and specificity of 94.1%. sCD163 can be considered a biomarker for pulmonary hypertension, early crisis prediction and monitoring hydroxyurea response in SCD patients. Elevated sCD163 in trait siblings could reflect increased risk of sickling in challenging situations.