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Tuberculosis: detection of Mycobacterium tuberculosis
Medical expert of the article
Last reviewed: 05.07.2025
Mycobacterium tuberculosis is normally absent from the material.
Unlike serological methods of diagnosing tuberculosis infection, which detect antibodies to Mycobacterium tuberculosis, PCR allows to detect directly the DNA of Mycobacterium tuberculosis and quantitatively express their concentration in the test material. The test material can be sputum, lavage fluid, urine, punctures from various organs and cysts, etc. The test has species specificity and high sensitivity (more than 95%). Microbiological diagnostics of tuberculosis is currently the main method for identifying patients and monitoring the effectiveness of treatment. However, microbiological tests for tuberculosis are extremely lengthy and have low sensitivity (the detection of positive samples does not exceed 50%). Diagnosis of tuberculosis using PCR has great diagnostic value (the study time is 4-5 hours). For DNA detection, it is enough for the test material to contain about 10 Mycobacterium. Detection of Mycobacterium tuberculosis DNA in the material using PCR is necessary in the following cases:
- rapid detection of the source of infection;
- diagnosis of pulmonary tuberculosis;
- diagnostics of extrapulmonary tuberculosis;
- monitoring the effectiveness of anti-tuberculosis treatment;
- early detection of relapses.
However, it should be noted that the use of PCR for the diagnosis of tuberculosis does not replace the bacteriological method.