Provided herein are methods for diagnosing the presence or the risk of development, or for the therapy control of vasculitis, in particular of large vessel vasculitis, like giant-cell arteritis (GCA), polymyalgia rheumatica (PMR), and Takayasu's arteritis, in a subject analyzing for the presence of antibodies against ferritin, in particular heavy chain ferritin or immunoreactive peptides thereof or ferritin analog protein, preferably bacterial ferritin analog protein, or immunoreactive peptides thereof, in a subject. In addition, test kits for use in the diagnosis of the presence or the risk of development, or for the therapy control of vasculitis, in particular of large vessel vasculitis, like GCA, PMR and Takayasu's arteritis, in a subject are also provided.