EP29 An evaluation of the use of baseline pulmonary function tests in the detection of interstitial lung disease in patients newly diagnosed with rheumatoid arthritis

Abstract

Background Interstitial lung disease (ILD) is a serious extra-articular manifestation of rheumatoid arthritis (RA). Risk factors include smoking, the presence of rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (CCP). Pulmonary function tests (PFT) show reduced carbon monoxide diffusion capacity (DLCO) early and reduced forced vital capacity (FVC) later in disease. HRCT is the gold standard diagnostic test while chest X-ray (CXR) has low sensitivity. PFT are routinely performed in the majority of RA patients at baseline at our tertiary centre. The aim of this study was to evaluate the frequency of abnormal PFT, specificity for ILD and influence on subsequent decision-making in patients newly diagnosed with RA. Methods A retrospective analysis was undertaken of patients with a new diagnosis of RA between January 2016 and December 2017. Patients meeting the ACR (2010) criteria for RA, with baseline PFT data available were included. Clinic letters and the hospital electronic records were used to obtain the data. Results 139 patients were included in the data analysis (Table 1). 23 patients had DLCO <70% predicted, while 7 patients had an FVC <80% predicted. Patients with abnormal PFT were more likely to be older, female, seropositive and to have smoked. Of the patients with DLCO <70%, CXR was abnormal in 6 patients with changes suggesting ILD in 2 patients. 13 patients had HRCT and 7/13 patients had evidence of ILD and 6/13 patients had significant emphysema on CXR or HRCT. 1 patient with DLCO of 82% had changes of ILD on a CT scan organised for another reason. Methotrexate was commenced in 19/23 patients with DLCO<70% and discontinued in 2 patients for respiratory reasons. Conclusion This evaluation suggests baseline PFT are more sensitive than baseline CXR in detecting ILD but that a DLCO <70% is not specific for this diagnosis. The abnormal PFT lead to HRCT being requested in 13/24 patients, of whom 7 had ILD which had not been identified by CXR in 5 patients. Baseline PFT are also useful as a reference point in patients who go on to develop respiratory symptoms at a later point in their illness. Disclosures A. Haque None. R. Kilding None. R. Smith None. S. Khalid None. R. Sandler None. M. Cox None. T. Hendry None. A. Flores-martin None. K. Lindop None. J. Maxwell None.