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Tuberculosis: antibodies to the tuberculosis pathogen in the blood
Medical expert of the article
Last reviewed: 05.07.2025
The diagnostic titer of antibodies to the tuberculosis pathogen in the blood serum is higher than 1:8.
The causative agent of tuberculosis is Mycobacterium tuberculosis. Tuberculosis is a widespread infection. The main method of its diagnosis is bacteriological examination (sensitivity is 80-85% for active pulmonary forms, 7-10% for renal tuberculosis). However, mycobacteria grow very slowly on nutrient media; to obtain even a preliminary answer in a bacteriological study, 3 weeks are required, which does not suit clinicians. In such cases, serological diagnostic methods are used until the answer is received from the results of the bacteriological study.
Determination of antibodies to the tuberculosis pathogen in blood serum is a new and very promising method of serological diagnosis of tuberculosis. The currently used bacteriological method of isolating mycobacteria tuberculosis requires significant time (from 4 to 8 weeks) and is very effective mainly in pulmonary forms of tuberculosis. The use of serological diagnostic methods, in particular ELISA, allows to significantly reduce the time of laboratory confirmation of the clinical diagnosis, actively use it for the diagnosis of extrapulmonary forms of tuberculosis, the method is especially valuable for the diagnosis of tuberculosis in children (difficulties 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 the specificity is 93%.
To detect antibodies to the tuberculosis pathogen of the IgA and IgG classes, rapid slide tests have been developed (the analysis is ready within 10 minutes) 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 tuberculosis pathogen in the blood serum allows only to form the necessary medical alertness of the clinician regarding tuberculosis infection (respiratory tuberculosis, extrapulmonary, genitourinary, osteoarticular tuberculosis), and to assess the intensity of post-vaccination immunity. This method cannot be used as the only basis for confirming the diagnosis.
What tests are needed?