MUC1 and granulomatosis with polyangiitis: The model (Figure 2) obtained an improvement of 57.1% for classifying MPA-ILD patients with a serum T0 KL-6 cut-off of 513 U/mL and 40% of improvement for classifying GPA non-ILD with a T0 serum KL-6 cut-off value of 513 U/mL and a T1 KL-6 cut-off of 301 U/mL.