Objective Recently, a genome-wide association study identified an association between RA-associated interstitial lung disease (ILD) and RPA3-UMAD1 rs12702634 in the Japanese population, especially for patients with a usual interstitial pneumonia (UIP) pattern. We aimed to replicate this association in a European population and test for interaction with MUC5B rs35705950.Methods In this genetic case-control association study, patients with RA and ILD and controls with RA and no ILD were included from France, the USA and the Netherlands. Only cases and controls from European genetic ancestries determined by principal components analysis were included in the analyses. RA was defined by the 1987 ACR or 2010 ACR/EULAR criteria and ILD by chest high-resolution CT scan, except in the control dataset from the Netherlands, where the absence of ILD was determined by chart review. Patients were genotyped for RPA3-UMAD1 rs12702634 and MUC5B rs35705950. Associations were tested using logistic regression adjusted for sex, age at RA onset, age at ILD onset or at certified absence of ILD, tobacco smoking status and country of origin.Results Among the 883 patients included, 322 were RA-ILD cases (36.5%). MUC5B rs35705950 was strongly associated with RA-ILD in all datasets {combined adjusted odds ratio [OR] 2.9 [95% CI 2.1, 3.9], P = 1.1 x 10-11. No association between RPA3-UMAD1 rs12702634 and RA-ILD was observed [combined OR 1.2 (95% CI 0.8, 1.6), P = 0.31. No interaction was found between RPA3-UMAD1 rs12702634 and MUC5B rs35705950 (P = 0.70).Conclusion Our findings did not support a contribution of RPA3-UMAD1 rs12702634 to the overall RA-ILD susceptibility in the European population.What does this mean for patients?Interstitial lung disease (ILD) can develop in 10-60% of patients with rheumatoid arthritis (RA) and is associated with an increased risk of death. We do not yet fully understand why RA-ILD occurs, but risk factors include genetics and environmental factors such as tobacco smoking. Identifying new genetic risk factors for RA-ILD may improve our understanding of how this disease occurs, help us categorize patients in terms of their risk level and help us to potentially identify new drug targets. A previous Japanese genetic study identified the RPA3-UMAD1 rs12702634 common genetic variant as a risk factor for RA-ILD. However, a second Japanese study failed to replicate these findings. In this international study including patients with European ancestry, we did not find that RPA3-UMAD1 rs12702634 contributed to the overall risk of RA-ILD. Our findings highlight the importance of conducting analyses that try to replicate the results of a study. We also emphasize that genetic associations-even those already reported-require rigorous testing in different groups of people before we can conclude that they contribute to disease risk. Ongoing collaboration and multi-ancestry genetic studies are essential in order to advance our understanding of the complex genetics underlying RA-ILD
