Diagnostic Value of Nanopia® KL-6 in Chinese Patients with Interstitial Lung Disease: A Prospective Multicenter Observational Study

Background: Krebs von den Lungen-6 (KL-6) is considered a sensitive biomarker for diagnosis of interstitial lung disease (ILD). We aimed to evaluate the diagnosis value of Nanopia® KL-6 (SEKISUI MEDICAL CO., LTD., Tokyo, Japan) in a Chinese cohort of patients with ILD. Methods: : Totally 451 patients were enrolled in our multicenter study, including 166 (36.8%) ILD patients, 210 (46.6%) non-ILD patients and 75 (16.6%) health controls. All ILD patients underwent high-resolution computed tomography (HRCT) followed by pulmonary function test (PFT). Serum KL-6 concentrations were measured by latex particle enhanced turbidimetric immunoassay (LTIA). Results: : KL-6 serum concentrations were significantly higher in ILD patients (911 U/ml, IQR 477-1790) than in non-ILD patients (225 U/ml, IQR 166-323) and health controls (196 U/ml, IQR 153-230, p<0.0001). Serum KL-6 higher than 435.5 U/ml appeared as the optimal cut-off value associated with ILD. KL-6 concentrations were inversely correlated with forced vital capacity (FVC) (rho=-0.515, p<0.001), total lung capacity (TLC) (rho=-0.563, p<0.001) and diffuse lung capacity of carbon monoxide (DLco) (rho=-0.544, p<0.001). ILD patients with more severe characteristics of HRCT including ground glass opacity, reticular pattern or honeycombing had significantly higher serum KL-6 levels. In the subgroup of ILD patients, serum KL-6 concentrations were higher in idiopathic interstitial pneumonia (IIP) patients (1024U/ml, IQR 697-2112.25) than in other ILD patients (743U/ml, IQR 702.75-2058.25, p<10-4). ILD and retained smoking were independent factors associated with higher KL-6 levels in multivariate analysis. Conclusions: : Our study confirms that KL-6 is a credible biomarker for the diagnosis of ILD in a Chinese cohort of patients. High serum KL-6 concentration should call attention to physicians to assess ILD with HRCT and PFT.