Idiopathic pulmonary fibrosis Significance of the usual interstitial pneumonia (UIP) CT-scan patterns defined in new international guidelines

International audienceIntroduction The new 2018 international guidelines for diagnosing usual interstitial pneumonia (UIP)/idiopathic pulmonary fibrosis (IPF) by CT scan split the old pattern possible UIP (2011 IPF guidelines) into two new patterns probable UIP and indeterminate for UIP. However, the proportions and prognoses of these new CT-scan patterns are not clear.Methods We used a monocentric retrospective cohort of 322 patients suspected of having IPF (University Hospital of Rennes; Competence Center for Rare Lung Diseases; 1 January 2012-31 December 2017). All patients initially diagnosed by CT scan as possible UIP were included. The chest CT-scans were then reclassified according to the new 2018 international guidelines by 3 observers. These data were then subjected to survival analysis with multivariate Cox regression using a composite endpoint of death, lung transplantation, a decline of ≥ 10% in forced vital capacity (FVC), or hospitalization.Results Of the 89 possible UIP patients included, 74 (83%) were reclassified as probable UIP and 15 (17%) as indeterminate for UIP. Probable UIP patients were more likely to meet the composite endpoint (56/74 [75.7%] vs. 5/15 [33%] patients; HR [IC 95%] = 3.12 [1.24; 7.83], P = 0.015). Multivariate analysis indicated that the probable UIP pattern was associated with significantly increased risk of reaching the composite endpoint (HR [95% CI] = 2.85[1.00; 8.10], P = 0.049).Conclusion The majority of possible UIP diagnoses corresponded to probable UIP, which was associated with a significantly worse prognosis than indeterminate for UIP. This distinction between these two CT patterns emphasizes the relevance of the new international guidelines for the diagnosis of IPF. © 2020 SPLF and Elsevier Masson SA