The present inventions relates generally to methods for diagnosing the presence or the risk of development or 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, in particular, in mammals. In addition, the present invention relates to 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. In particular, the present invention relates to a method for diagnosing 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 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. The presence of antibodies against ferritin or immunoreactive peptides thereof is indicative for 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 particular, detection of the presence of antibodies against ferritin or immunoreactive peptides thereof, allows early diagnosis of vasculitis, in particular of large vessel vasculitis, like GCA, PMR and Takayasu's arteritis.