Pertussis: antibodies to Bordetella pertussis in serum
Last reviewed: 23.04.2024
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The diagnostic titer of antibodies to Bordetella pertussis in the serum with RPGA is 1:80 and higher (in the unvaccinated).
The causative agent of whooping cough is Bordetella pertussis, a short stick with rounded ends, gram-negative, fixed. Most often ill children under 5 years old, adults often have atypical illness. The disease of whooping cough can be prevented if a vaccination against pertussis has been made. The main method of laboratory diagnostics is bacteriological (most cultures can be isolated in 90% of patients, the final answer is received on the 5th-7th day), direct immunofluorescence method is often used to detect Bordetella pertussis (sensitivity - 60-70%) and PCR (possesses 100 % sensitivity and specificity), serological methods are not suitable for early diagnosis of whooping cough.
RPGA is used to detect antibodies to Bordetella pertussis in serum. When testing in paired sera for confirmation of the diagnosis, it is necessary to obtain an increase in antibody titer 4 times or more (blood is taken for an interval of 10-14 days). Therefore, this method is suitable only for the needs of retrospective diagnostics.
In recent years, test systems have been developed that make it possible to determine antibodies of classes IgA, IgM and IgG to Bordetella pertussis antigens in serum by ELISA. IgM antibodies appear in the blood at the 3rd week from the onset of the disease, so they can be used to confirm the etiologic diagnosis. The dynamics of IgA antibody titer to Bordetella pertussis toxin is similar to that of IgM. IgG antibodies appear in the blood a little later, they can be found in the patient's blood for several years after recovery. The dynamics of different classes of antibodies to Bordetella pertussis in the serum is shown in Fig. 8-16. Determination of IgA, IgM and IgG antibodies is a screening test, it should be confirmed by the determination of antibodies to the antigen-toxin mixture (the actual virulent factor) and the hemoglutinin filament Bordetella pertussis in the serum by ELISA on the test strips (Western-blot method). The method has a specificity higher than 95%.
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