MUC1 and interstitial lung disease: In SYSTEM B, the KL‐6 level in the ILD group (1558, 726‐2772.5) was also significantly higher than those in the lung cancer group (315, 220.5‐449), other respiratory disease group (271, 171‐362), and control group (165, 150‐246; Kruskal‐Wallis H = 71.64, P < .01), but there was no statistically significant difference between the three groups (Figure 4B).