Clive Kelly

OBJECTIVES: The prevalence of interstitial lung disease (ILD) in RA is ∼5%. Previous work identified increasing age, active articular disease and articular damage as risk factors for RA-associated ILD (RA-ILD). The roles of high-resolution CT (HRCT) and lung function testing in defining the nature and extent of pulmonary involvement have recently been explored. This study is the first to examine predictive and prognostic factors for the development of RA-ILD and to report on the physiological and radiological characteristics of the condition from a large multicentre UK network. METHODS: We collected data from centres across the UK on patients with both RA and ILD (proved on HRCT) diagnosed over a 25-year period from 1987 to 2012 using a standard pro forma. Potential predictors of RA-ILD were analysed. Baseline lung function data were recorded and related to HRCT findings. We analysed HRCT for subtype and extent of lung involved and examined the relationship between these and both all-cause and pulmonary mortality. We compared our results with case controls matched for age and gender using computer-generated selection from the RA population from one contributing centre. RESULTS: A total of 230 patients were identified from across the UK with proven RA-ILD diagnosed over 25 years. Median age at diagnosis was 64 years and the male:female ratio was 1:1.09. Univariate analysis showed anti-CCP antibody titres to be the single most strongly associated predictor of RA-ILD. Male gender, age at onset, smoking and RF were all independently associated with RA-ILD on multivariate analysis. Vital capacity (VC) was preserved in limited disease but reduced in extensive disease, while gas transfer was reduced in both. Usual interstitial pneumonia (UIP) was the most common subtype on HRCT and both this and extensive disease were associated with increased all-cause mortality. CONCLUSION: This is the largest study of RA-ILD in the UK. Anti-CCP antibodies were strongly associated with RA-ILD in both sexes. Smoking was strongly associated with ILD in males, which may explain the higher frequency of RA-ILD in men. The predominant HRCT pattern was UIP and most patients had limited disease at presentation. The presence of UIP and extensive disease are associated with increased mortality. Baseline gas transfer is a useful screening tool for ILD, while the preservation of VC at baseline might predict limited disease on HRCT.

We performed high resolution computed tomography (HRCT) on the lungs of 20 patients with RA and clinical and radiological evidence of interstitial lung disease (ILD). A case control group of patients with RA but without evidence of ILD were similarly studied and all patients underwent detailed pulmonary function testing. Clinical findings, drug therapy, smoking status, the presence/absence of SS and disease activity were also assessed. HRCT showed a range of abnormalities among patients thought to have ILD. Interstitial fibrosis was confirmed in 16 but was frequently associated with emphysema. Ground glass opacification was present in seven, while basal honey-combing was also evident in seven patients. Both these features were present in two patients with ILD. Bronchiectasis was identified in six patients and was the predominant finding in two patients previously thought to have ILD. Among the control patients, HRCT was normal in only five. Clinically unsuspected ILD was present in four patients, while a further four had bronchiectasis. Pleural disease was identified in seven controls. Pulmonary function tests were generally poor predictors of HRCT findings, although a reduced residual volume (RV) [> 1 S.D.] was 83% specific for the presence of ILD and a raised RV [> 1 S.D.] was 64% specific for emphysema. Smoking did not correlate with the presence of either ILD or emphysema and there were no correlations between disease activity and HRCT findings. RA patients with evidence of ILD have abnormalities on HRCT which cannot be confidently predicted on any other non-invasive test.(ABSTRACT TRUNCATED AT 250 WORDS)