Przydatność badań serologicznych w analizie zachorowań na krztusiec w ognisku epidemiologicznym

Background Pertussis is a highly contagious respiratory disease. Neither vaccination nor past infection provides long-term immunity. Aim The analysis of the serological tests applicability for the diagnosis of pertussis in people from outbreaks. Material and methods After a case of pertussis had been confirmed in school student in Wroclaw, we analyzed the incidence of cough in her contact group. The study involved 91 people: 75 students and 16 teachers. Subjects were divided into 3 groups: with cough lasting ≥ 2 weeks, B. pertussis . The results of serological test were compared with a control group, composed of sera of 65 high school students from a school in another city, aged 13–16 years, who were diagnosed for rubella. Results Pertussis bacilli were isolated from one person – a teacher. 19/91 people (21%) were diagnosed with whooping cough. Comparison of serological results showed a significantly higher incidence of high IgG levels (≥ 80 U/ml) and positive IgA in patients with cough lasting over 2 weeks compared to the group without coughing (IgG 18/40 vs 4/41 [p = 0.006]; IgA 20/20 vs . 7/41 [p = 0.025]). None of diagnosed patients was suspected of pertussis. Among those with confirmed disease 15/20 patients had paroxysmal cough, 19/20 had night coughing. In the control group 13 people had positive IgG antibody titers and 3 had weakly positive IgA antibodies. Conclusions Single serological test (IgA i IgG) is useful in the diagnosis of Bordetella pertussis infections in patients from the outbreak. Whooping cough in vaccinated individuals proceeds as persistent cough.