WASHINGTON, DC — While it is established that interstitial lung disease (ILD) is linked with higher morbidity in patients with rheumatoid arthritis (RA), insights into the long-term progression of pulmonary impairment in such patients are lacking. Findings to be presented at the 2016 annual meeting of the American College of Rheumatology (ACR) will offer some initial clues.

Researchers at the Mayo Clinic in Rochester, Minnesota, conducted a study of 167 patients with a mean age of 67 years at the time of diagnosis, 62 of whom had never been smokers. For inclusion, patients had to have been evaluated for at least 4 weeks and had at least 1 pulmonary function test (PFT) during their care.

Patients were followed for a median time of 3.3 years after ILD diagnosis. The authors defined progression as a diffusing capacity of carbon monoxide (DLCO) <40%, being too ill to perform the test, or a predicted forced vital capacity (FVC) <50%.


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Approximately 53% of patients had usual interstitial pneumonia (UIP), while 42% had nonspecific interstitial pneumonia (NSIP), and 5% had RA-related organizing pneumonia (OP). The findings were as follows:

·         At the time of ILD diagnosis, baseline PFTs were: mean predicted FVC of 72% ± 20, forced expiratory volume (FEV1) of 72% ±21, and total lung capacity (TLC) of 73% ± 16, and DLCO of 55% ±18.

·         The mean predicted DLCO for UIP, NSIP, and OP were 51% ±16, 58% ±20, and 74% ±13, respectively (P=.006).

·         Over the follow-up period, 57 patients had reductions in DLCO to <40% predicted or were too ill to perform the test, and 29 patients declined to an FVC < 50%. 

·         Five years after ILD diagnosis, 33.2% of patients had DLCO <40% predicted or were too ill to perform the test, and 16.3% of patients had FVC <50% predicted.

·         Risk factors for progression to DLCO <40% included UIP (vs NSIP) (hazard ratio [HR]: 2.22; 95% confidence interval [CI]: 1.26, 3.92) and male sex (HR: 1.63; 95% CI: 0.96, 2.75).

·         C-reactive protein at the time of ILD diagnosis was linked with progression to FVC <50% (HR: 1.16 per 10 mg/L increase; 95% CI: 0.97, 1.38).

·         Higher baseline DLCO and FVC decreased the risk of progression to DLCO <40% and FVC <50%, and there was a significant association between the DLCO 6-month rate of change progression to DLCO <40% (HR: 1.55 per 10-unit decrease; 95% CI: 1.10, 2.18) and between the FVC 6-month rate of change and progression to FVC <50% (HR: 2.44; 95% CI: 1.44, 4.13). 

“We found that patients with UIP overall have higher risk of worsening lung function, and that patients with impaired air exchange–as reflected in the lower DLCO and worse pulmonary function at baseline–are more likely to progress,” said study co-author Eric L. Matteson, MD, MPH, chair of the Department of Rheumatology at the Mayo Clinic, told Rheumatology Advisor.

“This is especially true for patients in whom early decline is detected in the first months of disease. Patients with RA-ILD require particular attention to their cardiopulmonary status, and patients who have a rapid decline must be followed most closely,” he told Rheumatology Advisor.   

Dr Matteson suggests that future research in this area should aim to clarify the precise mechanisms involved in interstitial pulmonary fibrosis in RA and to predict which patients will develop progressive lung disease over the course of their disease. “Thus far, there are no definitive therapeutic options for RA-ILD, and this remains a major area of clinical need,” he said.

Reference

Zamora-Legoff A, Krause M, Crowson CS, Ryu JH, Matteson EL. Progressive decline of lung function in rheumatoid arthritis associated interstitial lung disease. Presented at: 2016 ACR/ARHP Annual Meeting. November 11-16, 2016; Washington, DC. Abstract 1497.

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