Molecular tests for TB detection: What’s new?

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Photo: UNDP/Turkmenistan

Drug-resistant tuberculosis remains a public health problem worldwide. The global tuberculosis (TB) eradication strategy provides guaranteed access of all patients with suspected tuberculosis to rapid molecular genetic testing. Most of the methods previously used to diagnose TB took long time from 48 hours to 4-6 weeks to get the test result. In addition, these methods are not always accurate, as they depend on how correctly the sputum was collected and how correctly it was delivered to the laboratory. The laboratory tests have also been done using several types of equipment.a

            The invention of the innovative molecular method GeneXpert (Cepheid, USA) made it possible to reduce the testing time to 2 hours with the minimum conditions and requirements for testing. It made a great positive change in the tuberculosis diagnosis. The technology makes it possible to identify the causative agent of tuberculosis and determine its resistance to Rifampicin – one of the main medicines for the tuberculosis treatment. Resistance to this drug is a marker or indicator of multidrug resistant tuberculosis (MDR-TB).   

            The “Xpert MTB / RIF” rapid molecular test has been available in Turkmenistan since 2013. With the support of the Global Fund grant, the National Reference Laboratory (Ashgabat city) and TB laboratories in all five velayats were equipped with this technology. Since 2020, it is planned to additionally install such platforms in remote etraps of the country, with a gradual coverage of the entire country until 2024.

            In 2018, Cepheid released a new “Xpert MTB / RIF Ultra” test, which is 10 times more sensitive than “Xpert MTB / RIF” and allows the detection of tuberculosis in a biological sample of a patient with a minimum bacterial quantity of up to 1-2 Mycobacterium tuberculosis in 1 ml of biological material. These tests are also available in Turkmenistan.

            In 2019, Cepheid developed more advanced “Xpert MTB / XDR” test, which allows to quickly perform an additional molecular drug susceptibility test for a wider range of anti-TB drugs within 90 minutes. The invention of this test will allow, in the shortest possible time, to obtain a result of sensitivity to the most common anti-tuberculosis drugs: isoniazid, amikcin, kanamycin, capreomycin and fluoroquinolones.

            In 2021, within the framework of the Global Fund grant to Fight AIDS, Tuberculosis and Malaria in Turkmenistan, it is planned to purchase new 10-channel GeneXpert platforms and “Xpert MTB / XDR” tests for the National Reference Laboratory and five provincial TB laboratories of the country.

            As a result of the introduction of a new molecular test, it is possible to achieve:

  • fast and accurate drug susceptibility test results;
  • reduce the testing time and to start the treatment within one to two days;
  • prescribe the right treatment and ensure a cure
  • adjust the treatment at the earliest stages to reduce loss of drugs due to inappropriate use;

    

Rapid drug susceptibility testing does not require high technical skills and complex infrastructure. Thus, this test will help healthcare specialists at all levels of the healthcare system more quickly and efficiently select the most appropriate TB treatment regimen for their patients.

 

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