Cumulative count of the different primary pulmonary function test (PFT) outcomes in longitudinal studies of systemic sclerosis-associated interstitial lung disease progression. Cumulative count of the different primary pulmonary function test (PFT) outcomes in longitudinal studies of systemic sclerosis-associated interstitial lung disease progression. Four studies which used forced vital capacity (FVC) but which did not make a distinction between absolute and % predicted values were excluded from this figure. DLCO: diffusing capacity of the lung for carbon monoxide; VC: vital capacity; RV: residual volume. Melissa Caron et al. Eur Respir Rev 2018;27:170102 ©2018 by European Respiratory Society