Soluble CD163 levels in children with sickle cell disease

Sickle cell disease (SCD) is characterized by vasculopathy, which has been causally linked to intravascular haemolysis and high levels of free plasma haemoglobin. Soluble CD163 (sCD163) is implicated in the clearance of free plasma haemoglobin and high plasma concentrations have been linked to arterial disease. We therefore investigated the value of sCD163 as a biomarker in children with SCD, and also measured haptoglobin levels in this population. We measured sCD163 in 25 control children with no haemoglobinopathy, 41 with sickle cell anaemia (HbSS) in the steady state, 27 with HbSS taking hydroxycarbamide, and 7 with HbSC disease. There was no significant difference between sCD163 levels in steady-state HbSS (1·78 mg/l) and controls (1·81 mg/l) (P = 0·86). However, sCD163 levels were significantly lower in those HbSS children taking hydroxycarbamide (1·35 mg/l) compared to both steady state HbSS (P = 0·004) and controls (P = 0·036). In children on hydroxycarbamide, sCD163 correlated negatively and highly significantly with percentage HbF (R = -0·76, P < 0·001), and this relationship was absent in those not taking hydroxycarbamide (R = 0·07, P = 0·65). sCD163 is a potentially useful biomarker in children with SCD, and may have a role in monitoring responses to hydroxycarbamide.