Factors associated with mortality in rheumatoid arthritis-associated interstitial lung disease: a systematic review and meta-analysis.

Background Interstitial lung disease (ILD) is a common and potentially life-threatening complication for rheumatoid arthritis (RA) patients. However, there is a lack of clear prognostic factors in rheumatoid arthritis-associated interstitial lung disease (RA-ILD) patients. The purpose of this study was to complete a systematic review and meta-analysis of the factors associated with mortality in RA-ILD patients. Methods Medline, EMBASE and the Cochrane Library were searched up to September 1, 2020. The Newcastle-Ottawa Scale (NOS) was applied to assess the methodological quality of the eligible studies. Study characteristics and magnitude of effect sizes were extracted. Then, pooled hazard ratios (HRs) with the corresponding 95% confidence intervals (CIs) and pooled risk ratios (RRs) with 95% CIs were calculated to assess the factors associated with mortality in RA-ILD. Results Twenty-three of 3463 articles were eligible, and ten factors associated with mortality for RA-ILD were evaluated in the meta-analysis. Older age (HRs = 1.04, 95% CI 1.03-1.05), male sex (HRs = 1.44, 95% CI 1.21-1.73), having a smoking history (HRs = 1.42, 95% CI 1.03-1.96), lower diffusing capacity of the lung for carbon monoxide (DLCO)% predicted (HRs = 0.98, 95% CI 0.97-1.00), forced vital capacity (FVC)% predicted (HRs = 0.99, 95% CI 0.98-1.00), composite physiological index (CPI) (HRs = 1.04, 95% CI 1.02-1.06), usual interstitial pneumonia (UIP) pattern on HRCT (HRs = 1.88, 95% CI 1.14-3.10 and RRs = 1.90, 95% CI 1.50-2.39), emphysema presence (HRs = 2.31, 95% CI 1.58-3.39), and acute exacerbation of ILD (HRs = 2.70, 95% CI 1.67-4.36) were associated with increased mortality in RA-ILD, whereas rheumatoid factor (RF) positive status was not associated. Conclusions Through this systematic review and meta-analysis, we found that older age, male sex, smoking history, higher CPI, lower DLCO% predicted, lower FVC% predicted, UIP pattern on HRCT, emphysema presence and acute exacerbation of ILD were associated with an increased risk of mortality in RA-ILD.