There is a lack of information on the natural history of patients with rheumatoid arthritis (RA) and associated interstitial lung disease (ILD). However, cryptogenic fibrosing alveolitis (CFA) is known to have a poor long-term prognosis. As part of a longitudinal prospective study, we compared baseline characteristics in 18 patients with RA-ILD and 18 patients with CFA matched for age, sex and symptoms. We wished to establish whether there were significant baseline differences in clinical, physiological or radiological parameters.
A diagnosis of ILD was confirmed by high-resolution computed tomography (HRCT) and supported by clinical and physiological findings in all patients. A number of clinical, immunological, physiological and radiological parameters were compared between the two groups. The median age in each group was 77 yr and 10 patients in each group were male.
Twelve of the RA patients had smoked in excess of 10 pack yr as compared with nine patients with CFA (not significant). Clubbing was found in five patients with RA-ILD and in 14 with CFA (P=0.008). Pulmonary function tests showed no significant differences between the groups in forced expiratory volume in 1s, vital capacity or gas transfer factor. HRCT showed more ground glass shadowing and peripheral disease in RA patients, but more established basal disease in those with CFA. Additionally, HRCT evidence of honeycombing was associated with an absence of rheumatoid factor and a low gas transfer factor.
Clubbing is more common in patients with CFA, while RA-ILD patients have a higher prevalence of rheumatoid factor. Together with the differences in baseline HRCT, these variables in two groups of patients with similar physiological impairment at baseline may be important predictors of outcome in the longer term.