Associations between shortened telomeres and rheumatoid arthritis-associated interstitial lung disease among U.S. Veterans

BACKGROUND

Shortened telomeres are associated with several different subtypes of interstitial lung disease (ILD), although studies of telomere length and ILD in rheumatoid arthritis (RA) are lacking.

METHODS

Within the Veterans Affairs Rheumatoid Arthritis (VARA) registry, we performed cross-sectional and case-control studies of prevalent and incident ILD, respectively. We randomly selected a subset of RA patients with ILD and individually matched them to RA patients without ILD according to age, sex, and VARA enrollment date. Telomere length was measured on peripheral blood leukocytes collected at registry enrollment using quantitative PCR (T/S ratio). Short telomeres were defined as a T/S ratio in the lowest 10th percentile of the cohort.

RESULTS

Our cross-sectional study cohort was comprised of 54 RA-ILD patients and 92 RA-non-ILD patients. T/S ratios significantly differed between patients with and without prevalent ILD (1.56 [IQR 1.30, 1.78] vs. 1.96 [IQR 1.65, 2.27], p < 0.001). Similarly, prevalence of ILD was significantly higher in patients with short vs. normal-length telomeres (73.3% vs. 32.8%, p = 0.002). Short telomeres were independently associated with an increased odds of prevalent ILD compared to normal-length telomeres (adjusted OR 6.60, 95% CI 1.78-24.51, p = 0.005). In our case-control analysis, comprised of 22 incident RA-ILD cases and 36 RA-non-ILD controls, short telomeres were not associated with incident RA-ILD (adjusted OR 0.90, 95% CI 0.06-13.4, p = 0.94).

CONCLUSION

Short telomeres were strongly associated with prevalent but not incident ILD among patients with RA. Additional studies are needed to better understand telomere length dynamics among RA patients with and without ILD.

Performance of Administrative Algorithms to Identify Interstitial Lung Disease in Rheumatoid Arthritis

OBJECTIVE

To determine the performance of administrative-based algorithms for classifying interstitial lung disease (ILD) complicating rheumatoid arthritis (RA).

METHODS

Participants in a large, multicenter RA registry were screened for ILD using codes from the International Classification of Diseases, Ninth Revision (ICD-9) and the ICD-10. Medical record review confirmed ILD among participants screening positive and a random sample of those screening negative. ICD and procedure codes, provider specialty, and dates were extracted from Veterans Affairs administrative data to construct ILD algorithms. Performance of these algorithms against medical record review was assessed by sensitivity, specificity, positive predictive value (PPV), negative predictive value, and kappa using inverse probability weighting to account for sampling methods.

RESULTS

Medical records of 536 RA patients were reviewed, confirming 182 (stringent definition) and 203 (relaxed definition) cases of ILD. Initially, we identified ≥2 ICD codes from inpatient or outpatient encounters as optimal discriminating factors (specificity 96.0%, PPV 65.5%; κ = 0.70). Subsequently, we constructed a set of ICD-9 and ICD-10 codes that improved algorithm specificity (specificity 96.8%, PPV 69.5%; κ = 0.72). Algorithms that included a pulmonologist diagnosis or chest computed tomography plus pulmonary function testing or lung biopsy had improved performance (specificity 98.0%, PPV 77.4%; κ = 0.75). PPV increased with exclusion of other ILD causes (78.5%) in comparison with the relaxed ILD definition (82.4%) and in sensitivity analyses (83.4-86.3%). Gains in specificity and PPV with greater algorithm requirements were accompanied by declines in sensitivity.

CONCLUSION

Administrative algorithms with optimal combinations of ICD codes, provider specialty, diagnostic testing, and exclusion of other ILD causes accurately classify ILD in RA.

Malondialdehyde-Acetaldehyde Adducts and Antibody Responses in Rheumatoid Arthritis-Associated Interstitial Lung Disease

OBJECTIVE

To compare serum anti-malondialdehyde-acetaldehyde (anti-MAA) antibody levels and MAA expression in lung tissue from patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) to those found in controls.

METHODS

Anti-MAA antibody (IgA, IgM, IgG) concentrations were measured in patients with RA-ILD and compared to those of RA patients with chronic obstructive pulmonary disease (COPD) and RA patients without lung disease. Associations between anti-MAA antibody with RA-ILD were assessed using multivariable logistic regression. Lung tissue from patients with RA-ILD, other ILD, or emphysema, and from controls (n = 3 per group) were stained for MAA, citrulline, macrophages (CD68), T cells (CD3), B cells (CD19/CD27), and extracellular matrix proteins (type II collagen, fibronectin, vimentin). Tissue expression and colocalization with MAA were quantified and compared.

RESULTS

Among 1,823 RA patients, 90 had prevalent RA-ILD. Serum IgA and IgM anti-MAA antibody concentrations were higher in RA-ILD than in RA with COPD or RA alone (P = 0.005). After adjustment for covariates, the highest quartiles of IgA anti-MAA antibody concentration (odds ratio 2.09 [95% confidence interval 1.11-3.90]) and IgM (odds ratio 2.23 [95% confidence interval 1.19-4.15]) were significantly associated with the presence of RA-ILD. MAA expression in RA-ILD lung tissue was greater than in tissue from all other groups (P < 0.001), and it colocalized with citrulline (r = 0.79), CD19+ B cells (r = 0.78), and extracellular matrix proteins (type II collagen [r = 0.72] and vimentin [r = 0.77]) to the greatest degree in RA-ILD.

CONCLUSION

Serum IgA and IgM anti-MAA antibody is associated with ILD among RA patients. MAA is highly expressed in RA-ILD lung tissue, where it colocalizes with other RA autoantigens, autoreactive B cells, and extracellular matrix proteins, highlighting its potential role in the pathogenesis of RA-ILD.