Improving our understanding of the role of conventional and novel biomarkers of disease activityCirculating biomarkers like IgG4, complement, eosinophilia and IgE might be useful for guiding management decisions but require further studyNovel imaging biomarkers might better classify patients into relevant disease groups with implications for treatment (e.g. might benefit from anti-fibrotic vs anti-inflammatory treatments). This evidence concerns the gene IGHE and Increased total eosinophil count.