GDF15 and idiopathic interstitial pneumonia: We validated these findings by examining a larger, independent cohort (34 controls and 98 IPF) utilizing an independent technique (quantitative ELISA) and found similar results with significantly higher levels of GDF15 in IPF patients (Fig. 6B; 1,666 pg/mL versus 475 pg/mL, P < 0.0001, Welch’s t test).