Changes in blood Krebs von den Lungen-6 predict the mortality of patients with acute exacerbation of interstitial lung disease

Acute exacerbation (AE) significantly affects the prognosis of patients with interstitial lung disease (ILD). This study aimed to investigate the best prognostic biomarker for patients with AE-ILD. Clinical data obtained during hospitalization were retrospectively analyzed for 96 patients with AE-ILD at three tertiary hospitals. The mean age of all subjects was 70.1 years; the percentage of males was 66.7%. Idiopathic pulmonary fibrosis accounted for 60.4% of the cases. During follow-up (median: 88 days), in-hospital mortality was 24%. Non-survivors had higher lactate dehydrogenase and C-reactive protein (CRP) levels, lower ratio of partial pressure of oxygen to the fraction of inspiratory oxygen (P/F ratio), and higher relative change in Krebs von den Lungen-6 (KL-6) levels over 1 week after hospitalization than survivors. In multivariable analysis adjusted by age, the 1-week change in KL-6—along with baseline P/F ratio and CRP levels—was an independent prognostic factor for in-hospital mortality (odds ratio 1.094, P = 0.025). Patients with remarkable increase in KL-6 (≥ 10%) showed significantly worse survival (in-hospital mortality: 63.2 vs. 6.1%) than those without. In addition to baseline CRP and P/F ratio, the relative changes in KL-6 over 1 week after hospitalization might be useful for predicting in-hospital mortality in patients with AE-ILD.