Serum osteoprotegerin and fibulin-1 levels negatively correlate with DLCO in IPF
Epidemiology, diagnosis and monitoringIdiopathic pulmonary fibrosis (IPF) and chronic hypersensitivity pneumonitis (cHP) are subtypes of interstitial lung disease characterized by excessive deposition of extracellular matrix (ECM). Assessing correct diagnosis and progression of fibrosis is essential for tailored patient care. As excessive ECM production is key in the pathogenesis, this study aimed at investigating whether levels of two ECM-related proteins in serum, osteoprotegerin (OPG) and fibulin-1 (FBLN1), could distinguish between patients with IPF or cHP and healthy controls and/or were related to severity, as measured by lung function impairment.
IPF/cHP diagnosis was confirmed by an interdisciplinary team according to current guidelines. Sera from healthy controls (n=14) and patients with IPF (n=11) or cHP (n=5) at the time of diagnosis were analysed for OPG by ELISA and FBLN1 by western blot.
OPG levels had a propensity to be higher in patients with IPF compared to cHP and healthycontrols, which was not seen for FBLN1. OPG levels correlated positively to FBLN1 levels in all patients (Pearson R=0.37, p=0.02), but not in healthy controls. Both OPG and FBLN-1 correlated negatively to the diffusing capacity to carbon monoxide (DLCO) in IPF patients only (R=-0.64, p=0.04 and R=-0.74, p=0.02 respectively). There were no differences in DLCO levels between IPF and cHP.
In this small cohort, OPG and FBLN-1 levels did not discriminate between control and IPF/cHP; however, the strong negative correlations between OPG/FBLN1 and DLCO in IPF patients, suggest possible value for staging disease severity. Further validation in a larger cohort is needed to confirm the potential of using OPG and FBLN-1 to stage fibrotic disease in IPF patients