Automatic quantitative computed tomography measurement of longitudinal lung volume loss in interstitial lung diseases

International audienceAbstract Objectives To compare the lung CT volume (CT vol ) and pulmonary function tests in an interstitial lung disease (ILD) population. Then to evaluate the CT vol loss between idiopathic pulmonary fibrosis (IPF) and non-IPF and explore a prognostic value of annual CT vol loss in IPF. Methods We conducted in an expert center a retrospective study between 2005 and 2018 on consecutive patients with ILD. CT vol was measured automatically using commercial software based on a deep learning algorithm. In the first group, Spearman correlation coefficients ( r ) between forced vital capacity (FVC), total lung capacity (TLC), and CT vol were calculated. In a second group, annual CT vol loss was calculated using linear regression analysis and compared with the Mann–Whitney test. In a last group of IPF patients, annual CT vol loss was calculated between baseline and 1-year CTs for investigating with the Youden index a prognostic value of major adverse event at 3 years. Univariate and log-rank tests were calculated. Results In total, 560 patients (4610 CTs) were analyzed. For 1171 CTs, CT vol was correlated with FVC ( r : 0.86) and TLC ( r : 0.84) ( p < 0.0001). In 408 patients (3332 CT), median annual CT vol loss was 155.7 mL in IPF versus 50.7 mL in non-IPF ( p < 0.0001) over 5.03 years. In 73 IPF patients, a relative annual CT vol loss of 7.9% was associated with major adverse events (log-rank, p < 0.0001) in univariate analysis ( p < 0.001). Conclusions Automated lung CT volume may be an alternative or a complementary biomarker to pulmonary function tests for the assessment of lung volume loss in ILD. Key Points • There is a good correlation between lung CT volume and forced vital capacity, as well as for with total lung capacity measurements (r of 0.86 and 0.84 respectively, p < 0.0001). • Median annual CT volume loss is significantly higher in patients with idiopathic pulmonary fibrosis than in patients with other fibrotic interstitial lung diseases (155.7 versus 50.7 mL, p < 0.0001). • In idiopathic pulmonary fibrosis, a relative annual CT volume loss higher than 9.4% is associated with a significantly reduced mean survival time at 2.0 years versus 2.8 years (log-rank, p < 0.0001)