Using Xpert MTB/RIF® to diagnose TB – is progress being made?

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A new study has investigated the market penetration of a key molecular test for diagnosing tuberculosis (TB), termed Xpert MTB/RIF® (Xpert; Cepheid, CA, USA). The results reveal that there has been good progress in the implementation of this diagnostic in high-burden countries since 2014, however more could be done.

By the end of 2016 approximately 23 million Xpert cartridges had been obtained by public sector in 130 of the 145 countries eligible for concessional pricing. Despite this, smear microscopy remains the most widely used test for TB in low- to middle-income countries, as study author Madhukar Pai (McGill Global Health Programs, Montreal, Canada) explained: “Xpert MTB/RIF is far superior to sputum smear microscopy, and yet smears continue to be the most widely used initial TB test.”

Researchers from McGill, the Stop TB Partnership (Geneva, Switzerland), FIND (Geneva, Switzerland) and KNCV (Den Haag, Netherlands) assessed National TB programs (NTPs), or their partnering organizations, in 22 high-burden countries. They obtained data and sought to assess dynamic trends from 2014–2015.

The results, published recently in the European Respiratory Journal, reported findings stating that the median smear/Xpert ratio, a statistic calculated by comparing the total smear volumes for initial diagnosis in 2015 with the number of Xpert cartridges procured in 2015 (for each country), has decreased over time.

Pai further elucidated their findings: “We tracked the market uptake of Xpert in 22 highest TB burden countries, and compared the trend between 2014 and 2015. Our data show that the 2015 data are better than 2014 – the median smear/Xpert ratio decreased from 33 to 9, 82% of countries expanded their algorithms to include more WHO-recommended groups, and 9% of countries further decentralised Xpert placement in healthcare systems compared with 2014.”

He concluded: “But a lot more can be done to reach scale. This will require the TB field to address both demand and supply side issues. A big concern is the low budgets of most NTPs. So, while all NTPs do have GeneXpert machines, they are under-using it by rationing the test only for a few, select groups (e.g., those at risk of MDR, people living with HIV), rather than make it freely available to all TB patients.

“Yes, the test is more expensive than smears, but much more accurate and very good at picking up drug-resistance. Early detection of TB and DR will help reduce transmission. So, If NTPs must consider cost-effectiveness rather than the dollar price of the test. If countries are serious about TB elimination, they need to invest more in TB control, and scale-up excellent new technologies such as Xpert.”

Want to find out more about the challenges facing diagnosis in tuberculosis? Read our interview with Madhukar Pai on ID hub now.

Source: Cabazon D, Suresh A, Oghor C et al. Implementation of Xpert MTB/RIF in 22 high tuberculosis burden countries: are we making progress? Europ. Resp. J.50 (1700918) (2017)

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