Tuberculosis: detection of mycobacterium tuberculosis

Last reviewed by: Aleksey Portnov , medical expert, on 31.05.2018

Mycobacterium tuberculosis in the material is normally absent.

In contrast to serological methods for diagnosing tuberculosis infection, detecting antibodies to mycobacteria of tuberculosis, PCR makes it possible to directly detect the DNA of mycobacterium tuberculosis and quantitatively express their concentration in the test material. The test material can be sputum, lavage fluid, urine, punctate from various organs and cysts, etc. The test has specific specificity and high sensitivity (more than 95%). Microbiological diagnosis of tuberculosis is currently the main method of identifying patients and monitoring the effectiveness of treatment. However, microbiological tests for tuberculosis are extremely long and have a low sensitivity (detection of positive samples does not exceed 50%). Diagnosis of tuberculosis by PCR is of great diagnostic importance (the time of the study is 4-5 hours). To detect DNA, it is sufficient that there are about 10 mycobacteria in the test material. Detection of the DNA of mycobacterium tuberculosis in the material by PCR is necessary in the following cases:

  • rapid detection of the source of infection;
  • diagnosis of pulmonary tuberculosis;
  • diagnostics of tuberculosis of extrapulmonary localization;
  • 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.

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