Bordetella pertussis, IgM antibodies

Why this test?

For serological laboratory diagnosis of whooping cough caused by Bordetella pertussis;

for the diagnosis of acute and current infection caused by Bordetella pertussis, starting from the second week after the appearance of the first clinical symptoms of the disease; 

for the diagnosis of acute and current infection in case of  children not vaccinated against whooping cough

In what cases is it prescribed? 

With clinical manifestations of whooping cough: dry spastic cough, paroxysmal, accompanied by a deep whistling breath, vomiting, cyanosis of the nasolabial triangle, acrocyanosis, weakness, dyspnea, lacrimation, body temperature is mostly normal, possible fever, in the clinical blood analysis - leukocytosis, relative and absolute lymphocytosis; 

when pertussis caused by Bordetella pertussis is suspected, starting from the second week after the appearance of the first clinical symptoms of the disease; 

during examination of people who were in close contact with patients with whooping cough;

in differential diagnosis with acute respiratory viral diseases, measles, bronchitis, pneumonia, bronchial asthma.

Test information  

Whooping cough is an acute anthroponous bacterial infection, one of the characteristic features of which is a long paroxysmal spastic cough. The causative agent is Bordetella pertussis, Bordet - Zhangou bacillus, a stationary small gram-negative coccobacillus belonging to strict aerobes. The infection is transmitted by airborne droplets. 

The source of infection is a sick person with any form of infectious process. The B. pertussis microorganism 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 - agglutininogens. 

Depending on the presence of agglutinogens of the 2nd and 3rd class in the bacterial cell, four serotypes of B. rertussis are distinguished. In addition to those described, the antigenic structure of B. pertussis includes hemagglutinins, adenylate cyclase hemolysin. In 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 or 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. A clinical blood test may show leukocytosis, relative and absolute lymphocytosis.

With a severe course of the disease, the development of complications is possible: impaired cerebral circulation, loss of consciousness, convulsions, emphysema of the lungs and mediastinum, atelectasis, bleeding, hernias, the addition of secondary infection with the development of bronchitis, pneumonia, pleurisy, otitis, mediastinitis. It should be noted that the most severe disease occurs in young children. It is characterized by a shorter incubation, long paroxysmal periods, the development of severe consequences and complications. In adults and persons after previous 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 indicators. In the clinical laboratory diagnosis of whooping cough, several methods are used: a bacteriological method to detect the growth of colonies of the pathogen, a serological method aimed at determining antibodies to B. pertussis antigens, a polymerase chain reaction method - to detect the genetic material of the pertussis pathogen.

The diagnosis is made upon confirmation by at least one of the specified methods. Serological examination allows to detect specific antibodies in the blood serum aimed at the antigens of the causative agents of B. рertussis. It is advisable to use serological diagnosis of whooping cough no earlier than the second week of the disease, the optimal times are from the 3rd to the 6th week of the disease. In the case of primary infection with the causative agent B. retussis, in the second week after the appearance of clinical symptoms of the disease, antibodies of the IgA and IgM classes begin to be synthesized.

Further, in the 3-4th week of the disease, the synthesis of IgG class antibodies begins, reaching the 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 an acute infection, IgM antibodies are determined at a low level, which may be associated with the formation of an immune response.