Immunologically, compared to the non-PF-ILD group, lower albumin level (non-PF-ILD vs. PF-ILD: 4.2 vs. 3.85 g/dL, p = 0.025) and less decline in IgG level at the 3rd month of follow-up (non-PF-ILD vs. PF-ILD: -14% vs. 0%, p = 0.026) were found in PF-ILD group with statistical significance (Table 2). Here, ALB is linked to interstitial lung disease.