MUC1 and idiopathic pulmonary fibrosis: Baseline KL-6 levels in patients with COVID-19 were comparable to those measured in a cohort of heart failure patients but statistically lower than serum levels measured in a mild to moderate cohort of IPF patients (baseline KL-6 COVID-19 365IU/ml (IQR 233–493) n = 67, heart failure 419 IU/ml (IQR 294–581) n = 20, IPF 1005 (IQR 514–1604 IU/ml) n = 20, Kruskal-Wallis, p<0.0001) (Fig 1).