LAUSR

OBJECTIVE To assess predictors of subclinical rheumatoid arthritis-associated interstitial lung disease (RA-ILD) using quantitative lung densitometry (qLD). METHODS RA patients underwent multi-detector row computed tomography scanning at baseline and after an average of 39 months. Scans were analyzed with qLD for the percentage of lung parenchyma with high attenuation areas (%HAA: the percentage of voxels of -600 to -250 Hounsfield units). Additionally, a pulmonary radiologist calculated an Expert Read Score (ERS) for RA-ILD features. Generalized linear models were used to identify indicators of baseline %HAA and predictors of %HAA change. RESULTS Baseline %HAA was assessed in 193 RA patients and 106 had repeat qLD assessment. %HAA was correlated with ERS (Spearman's rho = 0.261; p< 0.001). Significant indicators of high baseline %HAA (>10% of lung parenchyma with high attenuation) included female sex, higher pack-years of smoking, higher body mass index, and anti-CCP ≥ 200 units, collectively contributing an area under the receiver operator curve (AUROC)=0.88 (95% CI 0.81-0.95). Predictors of %HAA increase, occurring in 49% with repeat qLD, included higher baseline %HAA, presence of MUC5B minor allele, and absence of HLA-DRB1 shared epitope (AUC-ROC = 0.69; 95% CI 0.58-0.79). The association of the MUC5B minor allele with %HAA change was higher among men and those with higher cumulative smoking. Within the group with increased %HAA, anti-CCP level was significantly associated with a greater increase in %HAA. CONCLUSIONS %HAA, assessed with qLD, was linked to several known risk factors for RA-ILD and may represent a more quantitative method to identify RA-ILD and track progression than expert radiologist interpretation.