To compare the effectiveness of abatacept (ABA) in Rheumatoid Arthritis-associated Interstitial Lung Disease (RA-ILD) according to the radiological patterns of usual (UIP) or non-specific interstitial pneumonia (NSIP).

From an observational longitudinal multicentre study of 263 RA-ILD patients treated with ABA, those with UIP or NSIP were selected. Lung function, chest high resolution computerised tomography (HRCT) and dyspnoea were recorded and compared in both groups from baseline to the end of follow-up (progression definitions: improvement or worsening >10% of FVC or DLCO, changes in HRCT extension and 1-point change in the mMRC scale, respectively). Differences between final and baseline visits were calculated as the average difference (95% CI) through mixed effects models regression.

We studied 190 patients with UIP (n=106) and NSIP (n=84). General features were similar in both groups except for older age, positive rheumatoid factor, and previous sulfasalazine therapy, which were more frequent in patients with UIP. ILD duration up to ABA initiation was relatively short: median 16 [4-50] and 11 [2-36] months (p=0.36) in UIP and NSIP, respectively. Mean baseline FVC and DLCO were 82% and 63% in UIP and 89% and 65% in NSIP, respectively. Both parameters remained stable during 24 months with ABA. HRCT lesions and dyspnoea improved/stabilized in 73.1% and 90.5% and 72.9% and 94.6% of UIP and NSIP patterns, respectively.

ABA seems equally effective in stabilizing dyspnoea, lung function and radiological impairment in both UIP and NSIP patterns of RA-ILD. Early administration of ABA may prevent RA-ILD progression, regardless of the radiological pattern.