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Evaluation of a single-sample serological technique for diagnosing pertussis in unvaccinated children
C H Wirsing von König1, D Gounis, S Laukamp
1Institut für Hygiene und Labormedizin, Klinikum Krefeld, Germany. WvKoenig@t-online.de
Insights
Diagnosing pertussis (whooping cough) requires convalescent serum samples. Detecting IgG and IgA antibodies to pertussis toxin and filamentous hemagglutinin offers high sensitivity for pertussis diagnosis.
Area of Science:
- Immunology
- Infectious Diseases
- Pediatrics
Background:
- Pertussis (whooping cough) diagnosis can be challenging, especially in early stages.
- Serological markers, including immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies, are crucial for confirming Bordetella pertussis infection.
- Accurate diagnosis relies on sensitive and specific testing methods.
Purpose of the Study:
- To evaluate the diagnostic sensitivity of IgG and IgA antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) in a single serum sample.
- To determine the optimal timing and antibody combinations for pertussis diagnosis.
- To assess age-specific antibody responses in infants, toddlers, and school children.
Main Methods:
- Standardized enzyme immunoassay was used to measure IgG and IgA antibody levels to PT and FHA.
- Serum samples were collected from pertussis cases (n=525) and controls (n=321) at acute (1-3 weeks) and convalescent (5-10 weeks) phases.
- Specificity was set at 0.95 based on the 95th percentile of control group antibody levels.
Main Results:
- Acute serum samples showed low sensitivity (2-19%) for pertussis diagnosis.
- In convalescent samples, IgG anti-PT was the best single marker, with sensitivities of 61% (infants), 65% (toddlers), and 74% (school children).
- A combination of IgG anti-PT and IgA anti-FHA achieved high sensitivity (81-89%) for diagnosing pertussis from a single convalescent serum sample.
Conclusions:
- Serological testing for pertussis antibodies is most effective using convalescent serum samples taken 5-10 weeks post-symptom onset.
- Combining IgG anti-PT and IgA anti-FHA measurements provides a highly sensitive method for diagnosing pertussis from a single serum sample.
- Age-specific reference values are important for accurate interpretation of antibody levels in different pediatric age groups.
Abstract:
This study was performed to evaluate the sensitivity of immunoglobulin (Ig)G and IgA antibodies to pertussis toxin and filamentous hemagglutinin in diagnosing pertussis from a single serum sample. The pertussis group was defined according to the World Health Organization pertussis case definition. The control group coughed for 21 days or more but had no microbiological or serological evidence of Bordetella infection. Both cohorts were divided into infants (< 12 months of age), toddlers (1-4 years) and school children (5-10 years). There were 525 subjects in the pertussis group and 321 in the control group, with an even distribution of genders. IgG and IgA antibodies to pertussis toxin and filamentous hemagglutinin were measured in a standardized enzyme immunoassay. Antibody levels beyond the 95 percentile of the control cohort were regarded as indicative of recent contact, setting the specificity level at 0.95. Acute serum samples drawn between 1 week and 3 weeks after the onset of coughing showed a low sensitivity (2-19%) for diagnosing pertussis. In convalescent samples taken 5-10 weeks after the onset of symptoms, detection of IgG anti-pertussis toxin was the best single test, with a sensitivity of 61%, 65%, and 74% in infants, toddlers and school children, respectively. A combination of IgG anti-pertussis toxin and IgA anti-filamentous hemagglutinin using age-specific reference values had a sensitivity of 81-89% in diagnosing pertussis from a single serum sample taken 5-10 weeks after the beginning of symptoms.