Surfactant protein D as a marker for pulmonary complications in pediatric patients with sickle cell disease: Relation to lung function tests

Background Surfactant protein D (SP-D) is considered a candidate biomarker for lung integrity and for disease progression. Aim We determined the level of SP-D in children and adolescents with SCD and assessed its possible relation to pulmonary complications and lung function. Methods Serum SP-D levels were assessed in 50 SCD patients compared with 30 healthy controls. High-resolution computerized tomography (HRCT) of the chest was done. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC% and forced expiratory flow rate during 25-75% of expiration (FEF25-75%) were determined. Results SP-D was significantly higher in SCD patients than controls, particularly patients with sickle cell anemia than those with sickle beta-thalassemia. SP-D levels were significantly associated with increasing severity of interstitial lung disease. The highest SP-D levels were observed among patients with restrictive lung disease followed by mixed type then obstructive lung disease. SP-D was positively correlated to HbS and serum ferritin while negatively correlated to duration of hydroxyurea treatment and parameters of pulmonary functions. ROC curve analysis revealed that SP-D cutoff value 720 ng/mL could significantly detect the presence of abnormal pulmonary function among SCD patients with 82% sensitivity and 88% specificity. Logistic regression analysis showed that SP-D is an independent factor related to abnormal pulmonary function in SCD. Conclusions SP-D may be a promising biomarker for screening of SCD patients for risk of later pulmonary complications.