Seasonal variation of serum KL-6 concentrations is greater in patients with hypersensitivity pneumonitis

Background Serum KL-6 is a useful biomarker for the diagnosis of interstitial lung diseases (ILD). However, KL-6 has not been used to discriminate different types of ILD. Serum KL-6 concentrations can vary depending on antigen exposure levels in patients with hypersensitivity pneumonitis (HP); however, seasonal changes in serum KL-6 concentrations in ILD have not been determined. We hypothesized that seasonal variation of serum KL-6 is greater in HP than for the other ILD. The aim of this study was to determine seasonal variation of serum KL-6 concentrations in various ILD.