Based on stepwise multiple logistic regression analysis, high BAFF levels and high predicted DLCO were independent predictive factors for IPAF vs IPF (aOR = 1.23, 95% CI: 1.11–1.38, p < 0.001; aOR = 1.01, 95% CI: 1.00–1.02, p < 0.001) (Table 3). The gene discussed is TNFSF13B; the disease is idiopathic pulmonary fibrosis.