The method is based on the detection of Chlamydia trachomatis antigens in scrapings from the urethra, cervical canal and conjunctiva using the ELISA method with visual assessment of the result (sensitivity - more than 79%, specificity - more than 95%). This method is based on the presence of a genus-specific lipopolysaccharide antigen in chlamydia.
IgM antibodies are detected in the acute period of infection (as early as 5 days after its onset). The peak of IgM antibodies occurs in the 1st-2nd week, then there is a gradual decrease in their titer (as a rule, they disappear after 2-3 months even without treatment). IgM antibodies are directed against lipopolysaccharide and the main protein of the outer membrane of chlamydia.
IgM antibodies to Chlamydia pneumoniae, which are formed during primary infection and confirm the etiological diagnosis of the disease even with a single study, can be detected in the indirect immunofluorescence reaction or ELISA (sensitivity - 97%, specificity - 90%).
Gonococci cause purulent inflammation of the genital tract - gonorrhea. The difficulty of detecting them is 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 diagnosing Helicobacter pylori is the ELISA method. The method is non-invasive and indirect: antibodies to Helicobacter pylori, classified as IgA, IgM and (most often) IgG, are determined in the patient's blood.
ELISA allows to detect IgM and IgG antibodies to leptospires. IgM antibodies can be detected in the blood on the 4th-5th day of the disease, their titer reaches a peak on the 2nd-3rd week, then decreases over the course of months.
ELISA is a more sensitive and specific method for diagnosing tularemia, allowing detection of IgA, IgM and IgG class antibodies. Detection of IgM antibodies or a 4-fold increase in IgG titer confirms acute infection or reinfection in the presence of the corresponding clinical picture of the disease.
In Lyme disease, specific IgM antibodies usually appear in the blood 2-4 weeks after the onset of erythema migrans, with the peak of antibodies occurring at 6-8 weeks of the disease. In stage 1, IgM antibodies are detected in 40-60% of patients.
Determination of the titer of antibodies to the pseudo-tuberculosis pathogen in serum is a retrospective method for diagnosing pseudo-tuberculosis. Paired sera of the patient are examined. To detect specific antibodies, blood is taken for examination at the onset of the disease and 7-10 days after the initial examination.
Determination of antibodies to the yersiniosis pathogen is used to diagnose yersiniosis, including bacterial arthritis, Reiter's disease, Behcet's syndrome, and infectious arthropathies.
