Predictors of progression of HRCT diagnosed fibrosing alveolitis in patients with rheumatoid arthritis

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Abstract
Background: Fibrosing alveolitis (FA) is the most serious pleuropulmonary extra-articular feature of rheumatoid arthritis (RA). Features that predict progression of FA in patients with RA have not yet been determined. Objective: To identify clinical features that predict progressive FA in patients with RA. Methods: An unselected cohort of 29 patients with RA and FA confirmed by high resolution computed tomography (HRCT) were studied prospectively for 24 months. Three monthly clinical assessment, four monthly pulmonary function tests, and yearly HRCT scanning was undertaken on these patients. Progressive FA was defined as >15% fall in carbon monoxide transfer factor (Tlco) with evidence of increasing FA on HRCT or death as a result of FA. Results: During 24 months of follow up 10/29 (34%) patients had progressive FA. Progression on HRCT was seen as acute ground glass exacerbations or increasing reticular pattern lung involvement. Progressive FA was associated with the presence of bibasal crackles (p=0.041), Tlco (p=0.001), and extent (p=0.026) and distribution (p=0.031) of lung involvement on HRCT at initial presentation. When multiple logistic regression was used, only Tlco remained significant. Receiver operator curve analysis was employed to identify presenting Tlco of progressive FA. A Tlco <54% of the predicted value demonstrated 80% sensitivity and 93% specificity in predicting progressive FA. Conclusions: A Tlco <54% of the predicted value is a highly specific predictor of disease progression.