Understanding the determinants of health-related quality of life in rheumatoid arthritis-associated interstitial lung disease.

RATIONALE: Health-related quality of life (HRQL) is impaired among patients with interstitial lung disease (ILD). Little is understood about HRQL in specific subtypes of ILD.

OBJECTIVES: The aim of this study was to characterize and identify clinical determinants of HRQL among patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) and compare them to patients with idiopathic pulmonary fibrosis (IPF).

METHODS: We identified patients with a diagnosis of RA-ILD and IPF from an ongoing longitudinal cohort of ILD patients. HRQL was measured at their baseline visit using the Short Form Health Survey (SF-36), versions 1 and 2. Regression models were used to characterize and understand the relationship between selected baseline clinical covariates, the physical component score (PCS) and mental component score (MCS) of the SF-36.

MEASUREMENTS AND MAIN RESULTS: RA-ILD patients (n = 50) were more likely to be younger and female compared to IPF patients (n = 50). After controlling for age and pulmonary function, RA-ILD patients had a lower HRQL compared to IPF patients, as measured by the PCS (P = 0.03), with significant differences in two of four PCS domains - bodily pain (P < 0.01) and general health (P = 0.01). Clinical covariates most strongly associated with a lower PCS in RA-ILD patients compared to IPF patients were the presence of joint pain or stiffness and dyspnea severity (P < 0.01). Mental and emotional health, as measured by the MCS, was similar between RA-ILD and IPF patients.

CONCLUSION: The physical components of HRQL appear worse in RA-ILD patients compared to IPF patients as measured by the PCS of the SF-36. Differences in the PCS of the SF-36 can be explained in part by dyspnea severity and joint symptoms among patients with RA-ILD.