FRI0073 SEROLOGICAL PREDICTORS OF THE SEVERITY OF RHEUMATOID ARTHRITIS RELATED INTERSTITIAL LUNG DISEASE

Abstract

Background:The most common extra-articular manifestation of rheumatoid arthritis(RA) is interstitial lung disease (ILD). Although pulmonary manifestations in RA encompass the main airway, parenchyma, vasculature and pleura, ILD in particular, is associated with reduced survival. Up to 10% of RA patients suffer from clinically significant ILD while a substantial proportion have abnormal CT chest findings despite being asymptomatic.There are various biochemical and serological markers to predict the severity of the joints in RA. However, the clinical and laboratory determinants of RA related ILD (RA-ILD) are not well defined owing to the paucity of research data in this regard.Objectives:The main objective of this study is to determine the correlation between the rheumatoid factor (RF) serotypes and the severity of RA-ILD based on computer tomography (CT) findings.Methods: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. Participants were aged above 18 years, met the 2010 ACR/EULAR RA criteria, had RA for more than 6 months, were non-smokers, not pregnant and had no known chronic lung disease or lung malignancy based on their medical records. Seventy-two patients had ILD changes on HRCT of the chest and were included in this study. The CT images were scored based on a scoring system proposed by Kazerooni et al. Ground glass opacities represented the alveolar findings whereas honeycombing and septal thickening were the interstitial findings. The ground glass and fibrosis scores were on a scale of 0-5, with higher scores for greater involvement of the lobes. For each subject, the maximum ground glass and fibrosis scores were 25, respectively.Results:The frequency of RF positivity was comparable across the 3 serotypes (83.33-84.72%). The correlation between the clinical variables and the CT scores are listed in Table 1.We found that the the CT scores for ground glass showed significant positive correlation with disease duration (p=0.047)and IgA RF levels (p<0.050)whereas the fibrosis scores had significant relationship with multiple clinical covariates i.e age (p=0.004), disease duration (p=0.042), IgA RF levels (p<0.050), IgG RF levels (p=0.041) and anti-CCP levels (p=0.006). On multivariate analysis, only IgA RF levels remained significantly (p<0.05, standardized beta coefficient =0.604) associated with the ground glass scores. As for 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.Table 1.Correlation of CT scores with clinical covariates and antibodiesParametersGround glassFibrosisrp valuerp valueAge0.2290.0530.3340.004Disease duration0.2350.0470.2400.042Total MSS0.0580.6280.2240.145Cumulative Methotrexate dose0.0390.7480.0980.413Ig A0.608<0.050.576<0.05Ig M0.0530.6600.0190.873Ig G0.1830.1240.2410.041Anti CCP0.1170.3280.3190.006Conclusion:The IgA RF was the only serotype which was independently associated with the severity of RA-ILD.