Investigation of KL-6 levels in patients with IPF- OSA overlap syndrome: Preliminary results

Abstract

Circulating KL6 has been recognized as a biomarker of subclinical lung injury induced by oxidative stress in idiopathic pulmonary fibrosis (IPF) and in obstructive sleep apnoea (OSA). The proportion of coexistence of OSA and IPF is remarkable and IPF guidelines recently recognize OSA as a serious problem affected survival. The aim of this study was to investigate potential additive effects in serum and BALF KL6 levels, of the coexistence of OSA in IPF patients. 25 patients with IPF (Group A) and 22 patients with IPF-OSA(Group B) were included in the study. BALF KL6 was available in 13 patients from group A and in 10 patients from group B. We investigated the correlation of KL6 levels with several parameters from the sleep study, such as apnoea-hypopnoea index (AHI), REM apnoea-hypopnoea index (REM-AHI) and desaturation indexes. Both serum and BALF KL6 levels were non-significantly between two groups. However, a negative correlation was found between KL6 serum levels and severity of IPF, assessed by DLCO (r=-0.504, p=0.017) and KCO (r=-0.548, p=0.01), only in group with IPF plus OSAS. Our preliminary findings showed a negative association of serum KL6 and lung diffusion parameters only in IPF-OSA subgroup of patients. This evidence could support the hypothesis that KL6 levels probably reflect the additional oxidative stress OSA provides in IPF patients. Further studies are needed to clarify this observation.