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Tuberculosis: antibodies to the causative agent of tuberculosis in the blood
Last reviewed: 18.10.2021
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The diagnostic titer of antibodies to the causative agent of tuberculosis in serum is higher than 1: 8.
The causative agent of tuberculosis is Mycobacterium tuberculosis. Tuberculosis is a widespread infection. The main method for its diagnosis is bacteriological study (sensitivity - 80-85% with active pulmonary forms, 7-10% - with kidney tuberculosis). However, mycobacteria grow very slowly on nutrient media, to obtain even a preliminary answer for a bacteriological study, it takes 3 weeks, which does not suit clinicians. In such cases, serological diagnostic methods are used to obtain a response from the results of a bacteriological study.
Determination of antibodies to the causative agent of tuberculosis in serum is a new and very promising method for the serological diagnosis of tuberculosis. The currently used bacteriological method for isolating the mycobacterium of tuberculosis requires considerable time-consuming (4 to 8 weeks) and is very effective mainly in the pulmonary forms of tuberculosis. The use of serological diagnostic methods, in particular ELISA, allows to significantly reduce the time of laboratory confirmation of a clinical diagnosis, actively apply it for the diagnosis of extrapulmonary forms of tuberculosis. Especially valuable is the method for diagnosis of tuberculosis in children (difficulty in collecting sputum, multiple X-ray studies). The sensitivity of the ELISA method for the diagnosis of active forms of tuberculosis, regardless of localization, is 75%, and specificity is 93%.
For the detection of antibodies to the causative agent of tuberculosis classes IgA and IgG slides express tests (assay ready for 10 min) are developed based on the immunochromatographic method, its sensitivity is 350 IU / ml (IgA and IgG).
At the same time, it should be emphasized that the determination of antibodies to the causative agent of tuberculosis in the blood serum makes it possible to form only the due medical attention of the clinician to tuberculosis infection (respiratory tuberculosis, extrapulmonary, urogenital, osteoarticular tuberculosis), and evaluation of the intensity of postvaccinal immunity. This method can not be used as the only justification for confirming the diagnosis.
What tests are needed?