Line Immunoblot Testkit for the qualitative detection of Bordetella pertussis specific IgA- antibodies in human serum. The kit is used to detect a new, recent or long past infection with Bordetella pertussis or for differential diagnosis of longer lasting clinical manifestations with uncharacterised coughing. By virtue of the simultaneous detection of specific antibodies against pertussis-toxin (PT) and the catalytic part of the adenylate cyclase toxins (CatACT), the distinction between a Bordetella pertussis infection and a vaccination can be facilitated in most cases. Furthermore, the Line Immunoblot may provide evidence of possible infection with B. parapertussis. The absence of specific antibodies against PT and simultaneous presence of antibodies against CatACT and FHA may be regarded as evidence of B. parapertussis infection.