Bordetella pertussis, IgG antibodies

Why this test?

For serological laboratory diagnosis of whooping cough caused by the pathogen Bordetella pertussis,

For the diagnosis of acute and current infection caused by Bordetella pertussis, starting from the second week from the onset of the first clinical symptoms of the disease,

For the diagnosis of acute and current infection in children not vaccinated against whooping cough.

In what cases is it prescribed?

For serological laboratory diagnosis of whooping cough caused by the pathogen Bordetella pertussis,

to diagnose the current infection caused by Bordetella pertussis, starting from the 3-4th week from the onset of the first clinical symptoms of the disease,

to diagnose a past infection caused by Bordetella pertussis,

to diagnose current or past infection in children not vaccinated against whooping cough;

for the diagnosis of current or past infection in vaccinated children and adults with signs of severe seroconversion;

to evaluate the effectiveness of the vaccination against whooping cough.

Test information

Whooping cough is an acute anthroponotic bacterial infection, one of the characteristic features of which is a prolonged paroxysmal spasmodic cough. The causative agent is Bordetella pertussis, Bordet-Jangu bacillus, an immobile small gram-negative coccobacillus, which belongs to severe aerobes. The infection is transmitted by airborne droplets. The source of infection is a sick person with any form of infectious process.

The microorganism B. pertussis has a complex antigenic structure. The main antigenic targets for specific antibodies are pertussis toxin, surface protein - filamentous hemagglutinin, outer membrane protein pertactin, lipopolysaccharide, surface proteins - agglutinogens. Four serotypes of B. pertussis are distinguished depending on the presence of class 2 and class 3 agglutinogens in the bacterial cell. In addition to those described, the antigenic structure of B. pertussis includes hemagglutinins, adenylate cyclase hemolysin.

During the course of the disease, the following periods are distinguished: incubation (lasting from 3 to 14 days, on average 7-8 days), catarrhal (from 5-8 to 11-14 days), paroxysmal or spasmodic (from 2-3 to 6-8 weeks and more), the period of reverse development, or early convalescence (from 2 to 8 weeks), and convalescence (from 2 to 6 months). The most characteristic of whooping cough are manifestations that characterize the paroxysmal period of the disease. These include dry spastic cough, paroxysmal, cyanosis of the nasolabial triangle, acrocyanosis, possible vomiting, weakness, body temperature is mostly normal. In a clinical blood test, leukocytosis, relative and absolute lymphocytosis can be noted. With a severe course of the disease, complications may develop: cerebrovascular accident, loss of consciousness, convulsions, emphysema of the lungs and mediastinum, atelectasis, bleeding, hernia, secondary infection with the development of bronchitis, pneumonia, pleurisy, otitis media, mediastinitis. It should be noted that the disease is most severe in young children. It is characterized by shorter incubation, long paroxysmal periods, the development of severe consequences and complications. In adults and persons after prior vaccination, whooping cough may occur in a mild, atypical or erased form.

Diagnosis of whooping cough is based on epidemiological, clinical data and the results of changes in laboratory parameters. In the clinical laboratory diagnosis of whooping cough, several methods are used: a bacteriological method to detect the growth of pathogen colonies, a serological method aimed at determining antibodies to B. pertussis antigens, a polymerase chain reaction method to identify the genetic material of the whooping cough pathogen. The diagnosis is made upon confirmation by at least one of the indicated methods.

Serological examination allows the detection of specific antibodies in the blood serum directed to the antigens of pathogens B. pertussis. It is advisable to use serological diagnosis of whooping cough not earlier than the second week of the disease, the optimal time is from the 3rd to the 6th week of the disease.

In the case of primary infection with B. pertussis, in the second week from the onset of clinical symptoms of the disease, antibodies of the IgA and IgM classes begin to be synthesized. Then, at the 3-4th week of the disease, the synthesis of IgG class antibodies begins, reaching a maximum level by the 6-8th week and then gradually decreasing. A single detection of a high level of specific antibodies of the IgM class with various combinations of IgG or IgA indicates an acute or current infection in children and adults who have not been vaccinated. It should be noted that in some patients with acute infection, IgM antibodies are detected at a low level, which may be associated with the formation of an immune response.