A boarding school outbreak of pertussis in adolescents: value of laboratory diagnostic methods

Abstract

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.

Performance of Commercial Enzyme-Linked Immunosorbent Assays for Detection of Antibodies to Bordetella pertussis

“…These data suggested that values between 49 EU/ml and 94 EU/ml may be regarded as indeterminate and would need further confirmation. Using a Ն50-IU/ml cutoff may be especially useful in outbreak situations, where higher sensitivity is required (9). A recent summary from Denmark, Netherlands, and the United Kingdom comparing receiver operating characteristics (ROC) curves found that values between 60 IU/ml and 75 IU/ml gave the best single cutoff estimate (6a).…”

The impact of adolescent pertussis immunization, 2004–2009: lessons from Australia

“…3 School outbreaks were also frequent at this time. 10 Acellular vaccines replaced the Australian-manufactured wholecell vaccine for booster doses in 1997 and for all doses in 1999, and 95% coverage with three doses of this new vaccine (at 2, 4 and 6 months) by 2 years of age was attained within 4 years. 11 The availability of a well formulated triple vaccine with an acellular pertussis component (Boostrix [Tdap], GlaxoSmithKline, Brentford, England) and the recognition that pertussis incidence in adolescents was increasing prompted the National Immunisation Programme to begin using Tdap on 1 January 2004 instead of the reduced antigen diphtheria-tetanus (Td) booster dose previously recommended at age 15 to 17 years.…”

“…23 This is probably because of more frequent absences from school among older students and lower school retention rates (81% for grades [10][11][12] 26 and is likely to be applicable in comparable developed country settings.…”

Bordetella pertussis en estudiantes adolescentes de la Ciudad de México

“…5 Todavía, esta enfermedad no necesariamente tiene manifestaciones clínicas de tos persistente, sino que pueden encontrarse sujetos asintomáticos con Bordetella.…”