PDF pdf icon — k. In comparison, standard cultures can take 2 to 6 weeks for MTBC to grow and conventional drug resistance tests can add 3 more weeks. A sputum sample is collected from the patient with suspected TB. The sputum is mixed with the reagent that is provided with the assay, and a cartridge containing this mixture is placed in the GeneXpert machine. All processing from this point on is fully automated.
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The Genexpert test is a molecular test for TB. The Genexpert diagnoses TB by detecting the presence of TB bacteria, as well as testing for resistance to the drug Rifampicin.
It uses a sputum sample and can give a result in less than 2 hours. It can also detect the genetic mutations associated with resistance to the drug Rifampicin. A large scale demonstration project was then carried out in a number of different countries including South Africa and India to assess the implementation of the Genexpert. In December WHO endorsed the Genexpert technology and released a recommendation and guidance for countries to incorporate the new test into their programs.
When the WHO endorsed Genexpert it was expected that many similar tests would follow shortly afterwards. But progress has been slow, with a number of tests having been dropped. This test is a near Point of Care test, and it can be used in complementary circumstances where Genexpert cannot be used. There is more about Truenat. However the roll out proceeded slower than expected and it is believed that many customers delayed ordering as they expected the price to be reduced following the UNITAID announcement.
This causes problems for countries such as India, where initial diagnosis often takes place in the private sector. In addition to the cost of each test there is the cost of the Genexpert device. The device comes in different sizes providing for a different number of samples to be tested simultaneously. There are in addition costs for delivery and installation, and there is an annual servicing cost.
They did however say that they recognised the major resource implications of using it in this second way. WHO did also emphasize that the test does not eliminate the need for conventional microscopy culture and drug sensitivity testing, as these are still required to monitor treatment progress and to detect other types of drug resistance.
Further guidance was subsequently provided by WHO on the rapid implementation of the new test. It also represents new hope for the millions of people who are at the highest risk of TB and drug resistant disease. It is particularly unreliable when people are HIV positive.
Although culture gives a definitive diagnosis, to get the result usually takes weeks rather than the hours of the Genexpert test. The main advantage in respect of identifying rifampicin resistance, is again the matter of speed.
Normally to get any drug resistance result takes weeks rather than hours. A considerable number of articles have been written reviewing the use of the Genexpert test, and the WHO maintains a list of some of the major articles. Generally the views given are extremely variable, with some people considering that the test is extremely useful, as well as cost effective, and should be used in as many places as possible as soon as possible. Other people consider that it is not really suitable and practical at the present time for major use in low and middle income countries.
Other countries who had bought cartridges were Pakistan 21, , Kenya 20, , the Philippines 17, and Swaziland 16, By the end of September a total of Genexpert machines comprising 4, modules and 1,, cartridges had been purchased in 73 of the countries eligible for concessional pricing.
There was an increase in the purchase of cartridges in the third quarter of , which it is likely was associated with the drop in cartridge price around that time. By the use of the GeneXpert had expanded significantly.
In total 4. Between and more than 16 million tests had been carried out in countries. Subsequently a two year project took place to evaluate the use of the test at 18 sites across India. It has been said that it might not be as effective in India as elsewhere as the heat and humidity could affect the equipment.
The result could be that:. We have pilot projects at 18 sites going on to test its feasibility in the Indian situation where the climate and temperature conditions are different from the western countries.
In the Xpert Ultra assay was launched. It was found to be non-inferior to the standard Xpert MTB assay for the diagnosis of TB and the detection of rifampicin resistance and it can be used as an alternative to the latter in all settings. A new device called the GeneXpert Omni is currently under development. It is intended for point of care testing for TB and rifampicin resistance, using the same cartridges as those used in the current Genexpert machine.
It is expected that it will be smaller, lighter and less expensive than the current Genexpert. It will also come with a built-in 4 hour battery. This page was last updated in January Author Annabel Kanabus.
If you have found this page useful please tell other people about TBFacts. What is the Genexpert test? What is the involvement of Cepheid? The Genexpert can run a number of assays developed by the company Cepheid. Genexpert Test. Who developed the Genexpert test? When did the Genexpert test first become available? What is the cost of the Genexpert TB test? GeneXpert 4 module machine. Disadvantages The disadvantages include: The shelf life of the cartridges is only 18 months; A very stable electricity supply is required; The instrument needs to be recalibrated annually; The cost of the test; The temperature ceiling is critical.
Review articles A considerable number of articles have been written reviewing the use of the Genexpert test, and the WHO maintains a list of some of the major articles. Page Updating This page was last updated in January Would you like to send us a comment about this page? Tests TB.
The Genexpert test is a molecular test for TB. The Genexpert diagnoses TB by detecting the presence of TB bacteria, as well as testing for resistance to the drug Rifampicin. It uses a sputum sample and can give a result in less than 2 hours. It can also detect the genetic mutations associated with resistance to the drug Rifampicin. A large scale demonstration project was then carried out in a number of different countries including South Africa and India to assess the implementation of the Genexpert.
You are using an unsupported browser. Some features of this site may not function properly. For optimal user experience, please view this site in Chrome, Firefox, Safari, or Edge. Two-hour detection of MTB and rifampin resistance mutations. Each day, nearly 4, people lose their lives to TB and close to 30, people fall ill.
In comparison, standard cultures can take 2 to 6 weeks for MTBC to grow and conventional drug resistance tests can add 3 more weeks. Traditionally, tuberculosis is mostly diagnosed by a combination of chest X-rays, staining of sputum with special dyes followed by microscopy, growth of Mycobacterium tuberculosis in culture and the Mantoux test. The sputum smear microscopy is easily carried out and very cheap, and has been used for a long time by TB control agencies worldwide, combined with chest X-rays. However the test is not always accurate in HIV-positive patients, children, and patients with low bacterial load. The determination of drug susceptibility is particularly relevant because Mycobacterium tuberculosis becomes increasingly resistant to two of the major anti-tuberculosis drugs, isoniazide and rifampicin. This form of tuberculosis is called multi-drug-resistant tuberculosis MDR-TB is rapidly on the rise globally.