Horby P, Macintyre C R, McIntyre P B, Gilbert G L, Staff M, Hanlon M, Heron L G, Cagney M, Bennett C
Communicable Disease Surveillance and Response, World Health Organization, Ha Noi, Viet Nam.
Epidemiol Infect. 2005 Apr;133(2):229-36. doi: 10.1017/s0950268804003401.
Culture for Bordetella pertussis (B. pertussis) is the traditional gold standard for laboratory diagnosis of pertussis but is insensitive, especially later in the course of illness and in vaccinated persons. Interpretation of serology is limited by the lack of an appropriate reference standard. An outbreak of pertussis in a crowded boarding-school dormitory allowed evaluation of laboratory correlates of infection. Questionnaires, serum samples and throat swabs were collected from members of the exposed group. Serum samples from unexposed controls of a similar age group were used for comparison. B. pertussis PCR was performed on throat swabs, and sera were tested for IgA antibodies against whole-cell (WC) B. pertussis antigen and IgG antibodies to pertussis toxin (PT). The Centers for Disease Control and Prevention definition for pertussis was used to define clinical cases. We evaluated the use of a previously published cut-off for PT IgG of 125 EIA units (EU)/ml. Completed questionnaires were obtained from 115 students, of whom 85 (74%) reported coughing symptoms, including 32 (28%) who met the clinical case definition for pertussis. B. pertussis was detected by PCR in 17 (15%) and WC IgA in 22 (19%) students; neither correlated with symptoms, but dormitory of residence strongly predicted PCR status. The mean PT IgG geometric mean concentration, in this situation of high pertussis exposure, correlated with severity of symptoms and was significantly higher in both symptomatic and asymptomatic children exposed during the outbreak (P < 0.001) than in control children. A cut-off for PT IgG of 125 EU/ml was too high in an outbreak situation to be sensitive enough to identify pertussis cases. A case of pertussis in a crowded boarding-school dormitory resulted rapidly in an outbreak. Serology and PCR were useful in identifying the outbreak and commencing disease control measures. The use of serology has mostly been evaluated in community serosurveys, where it is not possible to determine if immunity reflects vaccination, asymptomatic disease or symptomatic disease. This outbreak gave us the opportunity to evaluate the value of serology and PCR in the presence of confirmed exposure to pertussis.
百日咳博德特氏菌（B. pertussis）培养是百日咳实验室诊断的传统金标准，但该方法不够灵敏，尤其是在疾病后期以及接种过疫苗的人群中。血清学检测结果的解读因缺乏合适的参考标准而受到限制。一所拥挤寄宿学校宿舍爆发的百日咳疫情，为评估感染的实验室相关指标提供了契机。研究人员从暴露组成员那里收集了问卷、血清样本和咽拭子。使用来自相似年龄组未暴露对照组的血清样本进行比较。对咽拭子进行B. pertussis聚合酶链反应（PCR）检测，并检测血清中针对全细胞（WC）B. pertussis抗原的IgA抗体以及针对百日咳毒素（PT）的IgG抗体。采用美国疾病控制与预防中心关于百日咳的定义来界定临床病例。研究人员评估了此前公布的PT IgG临界值125酶免疫分析单位（EU）/毫升的适用性。研究人员从115名学生那里获取了完整问卷，其中85名（74%）报告有咳嗽症状，包括32名（28%）符合百日咳临床病例定义的学生。通过PCR在17名（15%）学生中检测到B. pertussis，在22名（19%）学生中检测到WC IgA；二者均与症状无关，但居住宿舍强烈预示着PCR检测结果。在这种百日咳高暴露情况下，PT IgG几何平均浓度与症状严重程度相关，且在疫情期间暴露的有症状和无症状儿童中，该浓度均显著高于对照儿童（P < 0.001）。在疫情情况下，125 EU/毫升的PT IgG临界值过高，不够灵敏，无法识别百日咳病例。一所拥挤寄宿学校宿舍爆发的一例百日咳迅速引发了疫情。血清学检测和PCR检测在识别疫情及启动疾病控制措施方面很有用。血清学检测的应用大多是在社区血清学调查中进行评估的，在这种调查中无法确定免疫力反映的是疫苗接种、无症状感染还是有症状感染。此次疫情让我们有机会评估在确认暴露于百日咳的情况下血清学检测和PCR检测的价值。
