Xpert MTB/RIF: Will it help end TB ?

Dr Richa Sharma, CNS Correspondent, India
Photo credit: CNS: citizen-news.org
TB continues to scar the face of public health even today with India harboring the highest burden of TB cases in the world. The WHO Global Tuberculosis Report (2014) quotes 21 lakh as the estimated incidence of all forms of TB in India and 60,000 MDR-TB among notified cases. Recently there have been renewed efforts to address the scary upsurge of MDR-TB that is thwarting attempts of TB control in the global and Indian context.

In the face of such a serious condition, the time and sensitivity of the diagnosis plays a vital role especially in high burden settings like India.

In a recent webinar, hosted jointly by the International Union Against TB and Lung Disease (The Union) and CNS, Dr Sarabjit Chadha informed that, “Under India’s Revised National TB Control Programme (RNTCP), the standard protocol requires any person with presumptive pulmonary TB to undergo sputum smear microscopy and for smear negative cases, subsequent diagnosis needs to be done through repeated microscopy, radiology and clinical judgement. The entire process may take upto one year before accurate diagnosis of MDR-TB can be done--thus enhancing the time gap between diagnosis and initiation of treatment and thereby reducing chances of a successful tretament outcome”.

In such a scenario, an easy to use molecular diagnostic tool with disposable cartridges and with minimal scope for sample cross contamination, that provides results efficiently in 2 hours with a sensitivity rate of 97-100% not only for drug sensitive TB but also for rifampicin drug resistance, is nothing short of a miracle! And that is what XPert/MTB/RIF test is about. It not only aids in correct identification of TB and MDR- TB cases, but also helps in rolling out timely treatment.

A recent large scale study, covering a population of 8.8 million in India, has demonstarted that the introduction of Xpert MTB/RIF as initial diagnostic test for TB in public health facilities significantly increased case-notification rates of all bacteriologically confirmed TB by 39% and rifampicin-resistant TB case notification by five times.

However, as miraculous as it sounds and as real as it can get due to technological advancement, nothing good ever comes without a downside. It makes a lot of sense to use this WHO endorsed new diagnostic tool in tertiary centres and super specialty hospitals. However, some of the arguments advanced against installation of this high end diagnostic tool in the TB contact units at field level are:
  • The machine itself costs USD 20,000
  • The cost of one cartridge of Xpert MTB/RIF (and hence of 1 test) is as high as USD10
  • The bulky cartridges have a very short shelf life (18 months) and also need to be maintained at < 30 degrees centigrade, posing storage problems (all time air conditioning and hence constant electricity supply required)
  • The instrument needs to be recalibrated annually
  • Issues around safe disposal of large volumes of cartridges
Constant electricity supply and/or provision of temperature controlled storage can be a restraint in most low and middle income countries. I agree that most of these problems can be overcome through political will and the re-allocation, as well as restructuring, of the TB budget by the governments. Also, one has to keep in mind that many low and middle income countries are still struggling with acquiring sufficient quantity of second line drugs to treat cases of MDR-TB, and it will indeed be unethical to be able to diagnose MDR-TB timely and correctly but not be able to provide treatment. Governments will need to ensure a continuous supply of drugs before preparing to timely diagnose a large number of MDR-TB cases; they will need to complement the beneficial use of the Xpert MTB/RIF with availability of proper and adequate treatment services, as poor management of MDR-TB cases may inadvertently lead to XDR-TB-- a more severe form of TB. 

Thus, the scaling up of implementation needs to be thoroughly analyzed against the available resources and facilities, and the government needs to plan out a more feasible environment for the utilization of the existing tools available to combat MDR-TB.

Dr Richa Sharma, CNS Correspondent, India
21 July 2015