1. G-CSF, GM-CSF, IL-6, IL-15, sIL-2Rα, and BCA-1/CXCL13 have been identified as a novel biomarkers of disease activity in GCA and EGPA. 2. Differences of biomarker levels between diseases independent of disease activity, were more apparent than differences related to disease activity. Here, IL15 is linked to eosinophilic granulomatosis with polyangiitis.