Plasma surfactant protein-D as a potential biomarker in idiopathic pulmonary fibrosis

Objectives Idiopathic pulmonary fibrosis (IPF) is a disease of an increasing burden. Its diagnosis is based on definite high-resolution computed tomography pattern and is associated with the histopathological and/or radiological pattern of usual interstitial pneumonia with exclusion of other causes of interstitial pneumonia. The surfactant protein-D (SP-D) level in the serum is measured in several lung diseases, including IPF. Aim of study The aim of the current study is to assess the serum level of SP-D as a potential biomarker to distinguish between IPF and other idiopathic interstitial pneumonia patients. Patients and methods This study was conducted in the Chest Department, Kasr Al Ainy Hospitals, Cairo University. The study population included 20 healthy controls, 20 IPF patients, and 18 other idiopathic interstitial pneumonia patients. All were subjected to full history taking, clinical examination, high-resolution computed tomography chest, spirometry, arterial blood gases, blood samples for measuring SP-D by enzyme-linked immunosorbent assay. Results There was no statistical significance between the serum level of SP-D in IPF and non-IPF patients, however, there was a significant increase in the serum level of SP-D in IPF patients diagnosed at a late stage compared with those diagnosed at an early stage and those on anti-fibrotic therapy. Also, there was a statistical significance between the degree of clubbing and gastroesophageal reflux disease and the serum level of SP-D with a P value of 0.005 and 0.029, respectively. Serum SP-D level had a negative correlation with more severe form of the disease regarding the duration of illness, forced vital capacity percent, and it had a significant negative correlation with oxygen saturation and 6 min walk distance with a P value of 0.023 and 0.005, respectively. Conclusion The level of serum SP-D level in IPF patients correlate well with the severity of the disease and could be a possible marker to use for the follow up of patients on anti-fibrotic drugs.