Role of Autoantibodies in the Diagnosis of Connective-Tissue Disease ILD (CTD-ILD) and Interstitial Pneumonia with Autoimmune Features (IPAF)

Abstract

The diagnosis of interstitial lung disease (ILD) requires meticulous evaluation for an underlying connective tissue disease (CTD), with major implications for prognosis and management. CTD associated ILD (CTD-ILD) occurs most commonly in the context of an established CTD, but can be the first and/or only manifestation of an occult CTD or occur in patients who have features suggestive of an autoimmune process, but not meeting diagnostic criteria for a defined CTD—recently defined as “interstitial pneumonia with autoimmune features” (IPAF). The detection of specific autoantibodies serves a critical role in the diagnosis of CTD-ILD, but there remains a lack of data to guide clinical practice including which autoantibodies should be tested on initial assessment and when or in whom serial testing should be performed. The implications of detecting autoantibodies in patients with IPAF on disease behaviour and management remain unknown. The evaluation of CTD-ILD is challenging due to the heterogeneity of presentations and types of CTD and ILD that may be encountered, and thus it is imperative that immunologic tests are interpreted in conjunction with a detailed rheumatologic history and examination and multidisciplinary collaboration between respiratory physicians, rheumatologists, immunologists, radiologists and pathologists.

The interstitial lung disease multidisciplinary meeting: A position statement from the Thoracic Society of Australia and New Zealand and the Lung Foundation Australia

“…Although blood tests alone are rarely diagnostic of a specific ILD, certain autoantibodies are more specific for CTD such as anti‐CCP for rheumatoid arthritis; dsDNA and anti‐Smith antibodies for systemic lupus erythematosus; and anti‐topoisomerase (Scl‐70) for systemic sclerosis (scleroderma) . It should also be emphasized that amongst the clinical syndromes associated with myositis‐specific antibodies, lung manifestations can dominate in the absence of clinical myositis or rash …”

Treatment of idiopathic pulmonary fibrosis in Australia and New Zealand: A position statement from the Thoracic Society of Australia and New Zealand and the Lung Foundation Australia

“…Given that treatment of these conditions differs considerably from IPF, it is crucial that any patient with a fibrosing ILD undergo a thorough assessment including a detailed history of environmental exposures as well as specific questioning for subtle symptoms and signs of a CTD . Evaluation of autoantibodies as well as serum precipitins should also be considered in a compatible clinical context . The use of bronchoscopy and bronchoalveolar lavage is debated and should be considered on an individual basis .…”

Pleuroparenchymal fibroelastosis with positive MPO-ANCA diagnosed with a CT-guided percutaneous needle biopsy

“…However, pulmonary fibrosis can be associated with all CTDs and present in one setting, that is, pulmonary fibrosis with some autoimmune features but that does not fulfil criteria for a defined CTD, which was recently defined as ‘interstitial pneumonia with autoimmune features’ 8. Although autoantibodies have demonstrable usage in the diagnosis and management of patients with CTD-associated pulmonary fibrosis, there remains a lack of data to guide clinical practice 9. Because testing for MPO-ANCA is not recommend as a routine examination, there may be patients with both PPFE and MPO-ANCA positivity.…”