The method is based on the detection of Chlamydia trachomatis antigens in scrapings from the urethra, cervical canal and conjunctiva by ELISA with a visual evaluation of the result (sensitivity is more than 79%, specificity is more than 95%). This method is based on the presence in chlamydia of the rhodospecific lipopolysaccharide antigen.
IgM antibodies are detected in the acute period of infection (already 5 days after its onset). The peak of antibodies IgM falls on 1-2 weeks, then there is a gradual decrease in their titer (as a rule, they disappear after 2-3 months even without treatment). Antibodies of the IgM class are directed against the lipopolysaccharide and the main protein of the outer membrane of chlamydia.
Antibodies of class IgM to Chlamydia pneumoniae, formed during primary infection and confirming the etiologic diagnosis of the disease even in a single study, can be detected in the indirect immunofoulresence or ELISA (sensitivity - 97%, specificity - 90%).
Gonococci cause purulent inflammation of the genital tract - gonorrhea. The difficulty of their detection lies in their weak viability, which does not allow the bacteriological method to be widely used (it gives positive results in 20-30% of cases).
The most widely used serological method for the diagnosis of Helicobacter pylori is ELISA. The method is non-invasive and indirect: in the patient's blood, antibodies to Helicobacter pylori, attributed to IgA, IgM and (most often) IgG are determined.
ELISA allows detecting antibodies of classes IgM and IgG to leptospira. Antibodies of IgM class can be found in the blood on the 4th-5th day of the disease, their titer reaches a peak at the 2-3rd week, then decreases within months.
ELISA is a more sensitive and specific method of diagnosing tularemia, it allows detecting antibodies of classes IgA, IgM and IgG. Detection of IgM antibodies or a 4-fold increase in the IgG titer confirms an acute infection or reinfection with an appropriate clinical picture of the disease.
In Lyme disease, specific IgM antibodies usually appear in the blood 2-4 weeks after the onset of migratory erythema, the peak of antibodies occurs in the 6-8th week of the disease. In stage 1, IgM antibodies are detected in 40-60% of patients.
Determination of antibody titer to the causative agent of pseudotuberculosis in the serum is a retrospective method for diagnosing pseudotuberculosis. The paired sera of the patient are examined. To identify specific antibodies, blood is taken to the study at the onset of the disease and 7-10 days after the initial examination.
Determination of antibodies to the causative agent of yersiniosis is used for the diagnosis of yersiniosis, including bacterial arthritis, Reiter's disease, Behcet's syndrome, infectious arthropathies.
