Multicenter clinical investigation of pertussis in children and adolescents with persistent cough

Objective: Pertussis is an acute respiratory tract infection caused by Bordetella pertussis. This disease, though preventable by vaccination, the resurgence or persistence was reported frequently in developed countries. The current clinical epidemiology of pertussis in China is scarcely known. In this multicenter clinical study, we investigated the prevalence of pertussis in children and adolescents with persistent cough in Shanghai, Chongqing, Kunming and Yinchuan.

Methods: The nasopharyngeal swabs and serum (single) were collected from subjects aged ≥ 6 years with cough for more than 2 weeks during November 2008 to October 2009. The culture and multiplex PCR assays were used to identify the B. pertussis, and ELISA assay (Viron/serio, Germany) was used to test the antibody to pertussis toxin (PTIgG). The laboratory confirmed B. pertussis were culture positive and or PCR positive, and or PTIgG > 80 FDA-U/ml (single serum).

Results: Totally 1001 subjects were enrolled; 93.5% of subjects were immunized with diphtheria-pertussis-tetanus vaccine (DPT). The subjects were divided into group 1 aged from 6 to 8 years, group 2 (age -10 years), group 3 (age -12 years) and group 4 (age -18 years). The numbers of subjects of the four groups were 307, 249, 212, and 233; 113 subjects were B. pertussis positive (11.3%), 888 subjects were B. pertussis negative. The infection rates of the four groups were 7.2% (22, 307), 11.2% (28, 249), 10.4% (22, 212) and 17.6% (41, 233) respectively (χ(2) = 2915.2, P < 0.01). The total infection rate in Shanghai was 16.7% (65, 402), which was higher than that in the other regions (χ(2) = 3003.0, P < 0.01).

Conclusions: Although the immunization rates of DPT is high, B. pertussis infection is still an important etiological factor associated with persistent cough in children and adolescent. Doctors and the laboratory staff should pay attention to diagnosis of pertussis.