Biomarkers in interstitial lung disease: moving towards composite indexes and multimarkers?

Interstitial lung disease (ILD) covers a large spectrum of lung disorders that affects the parenchyma and is often associated with inflammation and/or fibrosis. Clinically, there is a great need for biomarker development for these disorders, to help diagnosis, treatment selection and assessment of efficacy as well as to predict progression. Thus far, no broadly validated biomarker exists for ILD, due to the existence of a very large number of disorders of often-unknown etiology, overlapping symptoms and disorders associated with a spectrum of multi-morbidities involving similar chronic inflammatory and fibrotic biochemical processes. We discuss here the development of biomarkers in IPF, sarcoidosis, connective tissue disease-associated ILD (CTD-ILD), and chronic hypersensitivity pneumonitis. We further discuss the need and opportunity to develop a multimarker approach that would be clinically meaningful for patients with ILD. Such composite index could include clinical symptoms, pathological assessment, and lung physiology measurements added to molecular information derived from bronchoalveolar lavage and serum. We also discuss the increased opportunity for patients to be involved in research as recent technological advances now allow the serial measurement of lung function using handheld spirometers, combined with handheld devices allowing measurement of patient reported outcomes, mobility, exercise, and sleep.