The most common extra-articular manifestation of rheumatoid arthritis (RA) is
interstitial lung disease (ILD). RA related ILD (RA-ILD) is associated with significant
morbidity and mortality. The main objective of this study was to determine the correlation between the rheumatoid factor (RF) serotypes and the severity of RAILD based on computed tomography (CT) findings. We recruited a total of 100 RA
patients who were tested for IgA RF, IgG RF and IgM RF and had high resolution
CT chest performed. Seventy-two patients had ILD changes on HRCT of the chest
and were included in this study. We found that the the CT scores for ground glass
showed significant positive correlation with disease duration and IgA RF levels
whereas the fibrosis scores had significant relationship with multiple clinical
covariates i.e age, disease duration, IgA RF levels, IgG RF levels and anti-CCP
levels. On multivariate analysis, only IgA levels remained significantly (p<0.05,
standardized beta coefficient = 0.604) associated with the ground glass scores.
Regarding the fibrosis scores, IgA RF levels and age were independent predictors
based on multivariate analysis after adjusting for confounders, with p scores of
<0.05 and 0.02, respectively. In conclusion, the IgA RF was the only serotype
which was independently associated with the severity of RA-ILD
