Quantitative assessment of interstitial lung disease in rheumatoid arthritis

Background: Interstitial lung disease (ILD) is the most common pulmonary affection of rheumatoid arthritis (RA). Patients with a severe RA-ILD extent i.e. >20% according to chest Computed Tomography (CT) semiquantitative (SQCT) scores, have poor prognosis. Quantitative CT (QCT) assessment with operator independent methods based on free software represents a reliable solution already tested in other ILD related to rheumatic diseases. Objectives: The main objective of this monocentric study is to verify if in RA-ILD there is a correlation between QCT and SQCT performed by experienced radiologists. Secondary aims are: (a) to explore if there is a difference of QTC indexes (QCTi) in RA-ILD patients with severe vs mild ILD extent; (b) to evaluate the discriminative ability of QCT in identifying severe RA-ILD patients. Materials and methods: The chest CTs of consecutive RA-ILD underwent to a SQCT assessment by two experienced chest radiologists. All CTs were also blindly post-processed by a rheumatologist in order to obtain the QCTi. QCTi correlations, distribution and discriminative ability were, respectively, verified using Spearman rank test, Mann–Whitney test and ROC curves. Results: The majority of QCTi showed a moderate degree (0.40 < r < 0.59) with SQCT assessment (p-value < 0.01). Patients with severe and mild ILD had dissimilar QCTi values (p = 0.001). Almost all of QCTi had a good discriminative ability (AUC from 0.73 to 0.81, p-value = 0.0001). Conclusions: These preliminary findings suggest that RA-ILD extent is related to QCTi. Moreover, QCTi can discriminate very well patients with a severe ILD. So, QCTi may become simple tools quickly estimate RA-ILD prognosis.