An infection with Yersinia enterocolitica may manifest in different ways either intestinal or extraintestinal. The selective laboratory detection of specific antibodies which are directed against secretory components of human pathogenic Yersinia strains is indicated especially for clinical suspicion upon post infectious, immune pathologic Yersiniosis complications like reactive arthritis, Erythema nodosum or Morbus Reiter. Because Yersinia specific antibodies of class IgG often also appear in serum of healthy patients the secure detection of Y. enterocolitica specific IgA antibodies is important in order to validate a supposed clinical Yersiniosis or to ensure another rheumatic complaints. These allow, in contrast to IgG antibodies, a relatively secure detection of an acute Yersinia infection.