Diagnosis of whooping cough: comparison of serological tests with isolation of Bordetella pertussis. A combined Scottish study.

Antibody titres for Bordetella pertussis in paired sera from 223 children with suspected whooping cough showed good correlation by complement fixation and agglutination techniques. The patient's age was related to serological responses and in a different way to B. pertussis isolations: in 73 children under 6 months of age B. pertussis was isolated from nasopharyngeal secretions in 42% and serological findings were positive in 19%; in 11 patients over 1 year of age serological tests were positive in 65% and cultures in 19%.B. pertussis was isolated from 59 out of 210 patients, while rising antibody titres were found in a further 43 from whom no isolations were made; thus 102 (49%) out of 210 showed evidence of infection with B. pertussis. Serotype 1,3 was the commonest serotype isolated from both immunized and unimmunized children. Previous immunization appeared to reduce the chances of isolating B. pertussis.