Abstract: A polypeptide of the formulaH--X.sup.1 --Gln--Thr--Art--Ala--Asn--Pro--Asn--Pro--Tyr--Thr----Ser--Arg--Arg--Ser-- Val--Ala--Ser--X.sup.2 --Yin which X.sup.1 and X.sup.2 each represents an optional coupling-facilitating amino acid residue, and Y represents --OH or --NH.sub.2, and an artificial compound in free or carrier-associated form with the capability of binding to glyco-conjugates, especially immunoglobulins, which compound is chosen from the group consisting of said peptide and functional analogues and functional derivatives thereof, are disclosed. Additionally, there is described an artificial pertussis toxin antigen, which mainly consists of at least one peptide sequence reacting with antibodies induced by the native pertussis toxin selected from the above polypeptide and parts thereof.

Abstract: A method for the diagnosis of whooping-cough is described. The method is carried out such that a sample of body fluid from a patient is incubated with at least a part of a pertussis toxin-sensitive, chromatophore containing fish-scale during a predetermined suitable period of time, that the fish-scale colour then is subjected to a first visual inspection, optionally by means of a microscope, that a substance inducing a colour change in the fish-scales is added, that the fish-scale colour then is subjected to a second visual inspection, optionally by means of the microscope and that the fish-scale colour first observed is compared with the subsequently observed fish-scale colour, the absence of a colour change, or a slight colour change, indicating the presence of pertussis toxin in the body fluid sample.A test kit for carrying the method into effect is described as well.