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Whooping cough: antibodies to Bordetella pertussis in the serum
Medical expert of the article
Last reviewed: 05.07.2025
The diagnostic titer of antibodies to Bordetella pertussis in serum with RPGA is 1:80 and higher (in unvaccinated individuals).
The causative agent of whooping cough is Bordetella pertussis, a short rod with rounded ends, gram-negative, immobile. Children under 5 years of age are most often ill; in adults, the disease often proceeds atypically. Whooping cough can be prevented if vaccinated against whooping cough. The main method of laboratory diagnostics is bacteriological (a culture can be isolated from a maximum of 90% of patients, the final answer is obtained on the 5-7th day), the direct immunofluorescence method is often used to detect Bordetella pertussis (sensitivity - 60-70%) and PCR (has 100% sensitivity and specificity), serological methods are not suitable for early diagnosis of whooping cough.
To detect antibodies to Bordetella pertussis in serum, RPGA is used. When testing paired serum samples, to confirm the diagnosis, it is necessary to obtain an increase in the antibody titer by 4 times or more (blood is taken for testing at intervals 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 allow the detection of IgA, IgM, and IgG antibodies to Bordetella pertussis antigens in blood serum using the ELISA method. IgM antibodies appear in the blood on the 3rd week from the onset of the disease, so they can be used to confirm the etiologic diagnosis. The dynamics of the IgA antibody titer to the Bordetella pertussis toxin are in many ways similar to that of IgM. IgG antibodies appear in the blood somewhat later; they can be detected in the patient's blood for several years after recovery. The dynamics of various classes of antibodies to Bordetella pertussis in the blood serum are shown in Fig. 8-16. Determination of IgA, IgM and IgG class antibodies is a screening test, it should be confirmed by determination of antibodies to a mixture of antigens - toxin (actual virulence factor) and Bordetella pertussis hemagglutinin filament in blood serum by ELISA on test strips (Western-blot method). The method has a specificity of over 95%.
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