Background/Purpose: Interstitial lung disease (ILD) is recognized as the most common pulmonary extra-articular manifestation of RA. The hazard ratio for 30-year risk of ILD in patients with RA (vs a matched cohort of patients without RA) is 8.96 (95% CI: 4.02, 19.94).¹ A recent meta-analysis concluded that anti-citrullinated protein antibody (ACPA) positivity was associated with an increased risk of lung disease (pooled odds ratio: 2.6).² The objective of this analysis was to evaluate the prevalence and incidence of ILD by ACPA levels in general and in the population with RA.

Methods: Data from July 1, 2002, to September 30, 2017, from administrative claims database Optum^® Clinformatics^™ Data Mart were used. Patients with ACPA test information were included in the analysis; the date of the test was the index date for the general cohort and first RA diagnosis date was index date for the RA cohort. The RA cohort comprised patients having ≥2 claims for RA and an ACPA test. Patients in the general and RA cohorts were divided into groups based on median ACPA titer values. Identification of patients with ILD was based on a published algorithm that included a two-step process: an initial diagnosis code of ILD, then a code for chest X-ray or CT scan on or after the first ILD diagnosis, and a second chest X-ray or CT scan after the first scan. Incidence rates (IRs) and prevalence rates were calculated for both cohorts and by subgroups based on ACPA levels.

Results: A total of 177,728 patients with ACPA information were identified (overall cohort); of those 20,746 (11.7%) and 156,982 (88.3%) were ACPA+ and ACPA−, respectively. A total of 9827 patients with RA had ACPA information (RA cohort); of whom 2927 (29.8%) and 6900 (70.2%) were ACPA+ and ACPA−, respectively. The prevalence of ILD in the overall cohort was 5.3% versus 8.2% in the RA cohort. The ILD IRs were higher in the ACPA+ versus the ACPA− group in the overall cohort (13.3 vs 8.4 per 1000 patient-years) as well as in the RA cohort (12.9 vs 11.7 per 1000 patient-years). In addition, the ILD IRs were greater for patients with higher ACPA titers in the overall cohort (Table 1).

Conclusion: The prevalence of ILD in patients with RA was higher than that in the general population. The ILD prevalence and IRs were higher in ACPA+ patients and increased with ACPA titer in the overall cohort. Further analysis with a larger RA cohort is required to confirm these findings.

References:

1. Bongartz T, et al. Arthritis Rheum 2010;62:1583–91.
2. Zhu J, et al. J Rheumatol 2014;41:1282−9.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/incidence-and-prevalence-of-interstitial-lung-disease-in-the-us-population-and-in-patients-with-ra-by-anti-citrullinated-protein-antibody-status/