An outbreak of pertussis occured over the past two years in Japan, and infection in adults as well as children has been noted. In adults, clinical recognition of this disease is difficult, because of the absence of typical clinical features. So the usefulness of the pertussis agglutination test for diagnosis was evaluated from the sera of 114 adults (66 healthy controls and 48 patients with persistent cough).
In the agglutination test two plus (++) has been usually used as the end titer in Japan. The range of titer for definite diagnosis of pertussis was statistically decided over 1:160 for B. pertussis serotype 1, 3; and 1:640 for serotype 1, 2. These levels are high compared with the data which was reported for children.
About half of the patients having persistent cough were diagnosed as pertussis from the agglutination test. In cases of adults, especially suffering from persistent cough at least for more than 2 weeks, pertussis should be taken into consideration and the agglutination test should be performed for definitive diagnosis.
