In patients with rheumatoid arthritis (RA) who develop interstitial lung disease (ILD), the pattern of ILD depends on the age at RA diagnosis and on the duration between the diagnosis of RA and the diagnosis of ILD. A retrospective, single-center study on the topic was conducted at a tertiary care center. Results of the analysis were published in the journal ERJ Open Research.
The researchers sought to assess the duration of RA as a risk factor for ILD, and to establish whether the duration of RA and age correlated with a radiologic pattern of nonspecific interstitial pneumonia (NSIP) or usual interstitial pneumonia (UIP). The database used in the study evaluated all patients with a diagnosis of RA-ILD, with a radiologic UIP or NSIP pattern, from 2000 to 2014, which involved a total of 137 patients. Those patients without sufficient data available to establish a date of ILD diagnosis were excluded from the analysis, with the final cohort comprising 121 participants.
The data of ILD diagnosis was defined as “the earlier between the first report of ILD on imaging, the first date an outside pulmonologist confirmed a diagnosis of ILD or the first visit with an ILD specialist.” A concomitant diagnosis of RA and ILD was defined as “both conditions being diagnosed within a year of each other to account for the time from symptom onset to diagnosis.”
The mean age at RA-ILD diagnosis was 63 years of age, which did not differ in those with UIP or with NSIP. Overall, 51% of the participants were men; 61% were current or former smokers. Based on high-resolution computed tomography, patients with UIP had higher rheumatoid factor titers and were more likely to have smoked compared with those with NSIP. Those with RA-UIP were diagnosed at a significantly older age than those with RA-NSIP (53.5±16 years vs 45.6±14 years, respectively; P =.01), with this difference remaining significant after accounting for sex and smoking (P =.001).
The range in age at diagnosis of ILD was similar in the RA-UIP and RA-NSIP arms. A significant percentage of patients had ILD that either predated (10%) or was concomitant with (17%) the diagnosis of RA. In addition, 49% of participants developed ILD either before or within 5 years of their RA diagnosis, and 67% of participants developed ILD either before or within 13 years of their RA diagnosis.
The duration of RA before ILD diagnosis was evaluated only in the 109 participants whose ILD diagnosis was concomitant with or following their diagnosis of RA. Mean duration of RA before an ILD diagnosis was 12.4 years. UIP was diagnosed significantly closer to the onset of RA than was NSIP (10.6 years vs 18.3 years, respectively; P =.025), with this difference remaining significant when controlling for such confounders as sex and smoking status (P =.011).
UIP was the pattern of ILD observed in 84% of participants whose ILD was diagnosed before or concomitantly with RA. When ILD was diagnosed15 years or more following an RA diagnosis, participants were significantly more likely to have NSIP than UIP (P =.039).
A major limitation of the current study is the fact that it was a retrospective evaluation of patients assessed at a tertiary care referral center, which may not be representative of patients typically seen in a community-based pulmonary practice.
The researchers concluded that although they are currently unable to reliably predict those patients with RA who will develop ILD, the knowledge that ILD clusters around the time of RA diagnosis, with a strong predilection for the seventh decade of life, can assist physicians in rendering a timely diagnosis of ILD in those at-risk patients with RA.
Mohning MP, Amigues I, Demoruelle MK, et al. Duration of rheumatoid arthritis and the risk of developing interstitial lung disease. ERJ Open Res. 2021;7(1):00633-2020. doi:10.1183/23120541.00633-2020