Serum-surfactant SP-D correlates inversely to lung function in cystic fibrosis

BackgroundCystic fibrosis (CF) affects the lungs causing infections and inflammation. Surfactant protein D (SP-D) is an innate defense lectin primarily secreted in the lungs. We investigated the influence of the SP-D Met11Thr polymorphism on CF lung function; and serum SP-D as a marker for CF lung disease.MethodsFor 107 CF patients (73 children, and 34 adults) serum SP-D and SP-D Met11Thr genotype were available. Leukocyte count was obtained for a subset of patients. Lung function was measured as forced expiratory volume in one second (FEV-1).ResultsSerum SP-D was increased in CF patients compared to healthy controls, positively correlated to leukocyte count, and negatively correlated to FEV-1. We found no correlation between SP-D Met11Thr genotype and FEV-1, and we found corresponding genotype frequencies in CF patients and in healthy controls.ConclusionSerum SP-D in CF patients was increased in parallel with leukocyte count and with reduced FEV-1 and may constitute an alternative biomarker for lung disease, in the clinical setting and in research.