Anti-B. pertussis Toxin IgM
The detection of specific IgM and IgA antibodies is used in the diagnosis of acute infection. IgA antibodies in combination with the corresponding symptoms indicate an active infection. The detection of IgM antibodies is particularly useful for diagnosis in young children, in whom the IgA response is often reduced or absent. According to WHO definitions, the increase in levels and IgG and / or IgA antibodies to one or more Bordetella pertussis antigens in unvaccinated children confirms the presence of whooping cough. For optimal laboratory diagnosis of whooping cough in children, two methods of investigation should be used simultaneously: sowing of material from the nasopharynx and determining the level of specific antibodies of class G, A and M to two toxins (CT and PHA) by means of an enzyme immunoassay (ELISA). In the presence of typical clinical manifestations, ELISA confirms the diagnosis, and with erased and atypical forms of infection, this method may be crucial.
Antibodies IgM - appear first in response to the introduction or reactivation of the pathogen, so they can identify the acute stage of the primary infection (when there is no IgG yet) or reactivate the chronic (against the background of detection of IgG). These antibodies do not have strict specificity, and therefore can be false positive, especially during pregnancy. This must be taken into account when interpreting a positive result. The length of the detection period in the blood for a primary infection, on average, is up to 3 months, with reactivation - from several days to several weeks.