High BAFF levels and high predicted DLCO are independent predictive factors for CTD-ILD vs IPF (aOR = 0.87, 95% CI: 0.79–0.95, p < 0.001; aOR = 0.99, 95% CI: 0.98–0.99, p < 0.001). The gene discussed is TNFSF13B; the disease is interstitial lung disease.