Multi Drug Resistant TB is often abbreviated to MDR-TB and it is a particular type of drug resistant TB. It means that the TB bacteria that a person is infected with are resistant to two of the most important TB drugs, isoniazid (INH) and rifampicin (RMP). If bacteria are resistant to certain TB drugs this means that the drugs don’t work. Other drugs then need to be taken by the person if they are to be cured of TB.
People with RR-TB are resistant to rifampicin. They may or may not have resistance to other drugs. MDR/RR-TB means patients with MDR-TB as well as patients with TB resistant to rifampicin.
For many years Multi Drug Resistant TB has been the most basic form of drug resistant TB, and the type of TB for which many statistics were collected. Then in 2016 RR-TB started to become more widely discussed because many people are now being diagnosed with TB using the GeneXpert test. The GeneXpert test detects resistance to rifampicin as well as resistance to isoniazid.
There are two main ways that you can get MDR TB or RR-TB. Firstly you can get it if you don’t take your drugs exactly as you have been instructed to by your health care provider. You may also get it if you are not taking the correct drugs. This could possibly be because your bacteria are resistant to more drugs than your health care provider realised. Maybe you have undiagnosed XDR-TB. This is referred to as acquired TB.
You can also get MDR or RR-TB if you become infected with TB bacteria from another person who already has MDR or RR-TB. This is known as primary TB. It used to be believed that most people have acquired TB, but now it is realised that many more people than were previously realised have primary TB.
Globally in 2016 about 490,000 people are estimated to have become ill with MDR-TB. In addition there were an estimated 110,000 people who had rifampicin resistant TB (RR-TB). So the number of people estimated to have had MDR-TB or RR-TB in 2016 was 600,000. Almost half of these cases (47%) were in India, China or the Russian Federation. There is more about TB in India and TB in China.
MDR-TB accounts for about 4.1% of new TB cases. Also, about 19% of previously treated TB cases were estimated to have either rifampicin or multi drug resistant TB in 2016.
About 6.2% of MDR-TB cases in 2016 had additional drug resistance, which means that they may have had what is known as extensively drug resistant TB (XDR). This is lower than the figures for previous years (9.5% in 2015, 9.7% in 2014). This decrease is most likely due to improved measurements, rather than an actual decrease.
In 2016 MDR-TB and RR-TB caused approximately 240,000 deaths. This is similar to the best estimate for 2015.
It is estimated that there is a large pool of undiagnosed drug resistant infection in children. It is considered by some people that this may be as high as 2 million children. Of the estimated 850,000 children that developed TB in 2014, 25,000 probably had MDR TB.1Dodd,P “Global burden of drug-resistant tuberculosis in children: a mathematical modelling study”, the Lancet, 2016, www.thelancet.com/journals/laninf/article/PIIS1473-3099(16)30132-3/abstract There is more about TB in Children.
The number of people actually reported (notified) to the World Health Organisation (WHO) as having MDR-TB or RR-TB was 26% of the people estimated to have become ill. This was about 153,119.
Among MDR/RR-TB patients notified in 2016, 39% were tested for resistance to both fluoroquinolones and second line injectable agents, a slight increase from 36% in 2015. Coverage varied widely among countries.
The notification numbers among different WHO regions for 2016 are shown in the table below.
|Region||Total notified TB cases||MDR-TB & RR-TB cases notified|
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There are some more TB statistics
In May 2016 a major change took place in the recommended treatment for drug resistant TB. Previously treatment for drug resistant TB had often required a large number of drugs to be taken taken for up to two years. Also the drugs often caused severe side effects in patients. So various efforts were being made to develop shorter regimens which were easier to take.
The first shorter and easier to tolerate regimen is known as the Bangladesh regimen. It appears to have a higher cure rate than “standard” MDR-TB regimens. In May 2016 the WHO recommended that there should be a major change to the treatment for drug resistant TB with shorter regimens being made available for many patients. There is more about the treatment of drug resistant TB.
By June 2017 89 countries were known to have imported or started using bedaquiline and 54 countries had used delamanid. Most of the patients treated with bedaquiline were reported by the Russian Federation and South Africa.
The latest data reported to WHO shows a treatment success rate for MDR-TB of only 54% for patients starting treatment in 2014. In 8% of patients the treatment failed, 16% died, 15% were lost to follow-up and 7% had no outcome information. This data is obtained by countries having groups of people (known as cohorts) who started treatment at a particular time and who are then followed for a number of years.
Although they are improving globally and in some countries, the treatment success rates for drug resistant TB are considered by WHO to be unacceptably low.
A total of 129,689 patients were enrolled on MDR-TB treatment in 2016 (up from 125,629 cases in 2015). However, this represents only about 22% of the estimated total number of cases (600,000) in 2016. Ten countries accounted for about 75% of the gap between enrollment in treatment and the estimated number of cases. China and India accounted for about 39% of the total gap.
In addition this total of 129,689 patients starting treatment was not even the total number of patients notified (153,119) in 2016. The numbers notified exceeded 90% in 14 high MDR-TB burden countries and the WHO European Region and the Region of the Americas. However it was much lower in the WHO African and Western Pacific Regions. Enrollments represented less than 60% of the number of notified cases in two high burden countries in 2016, China (50%) and South Africa (59%). These low percentages show that:
progress in detection is outstripping the capacity to provide treatment. In these settings the risk of transmission of drug resistant TB is very high.
Once patients have been diagnosed with drug resistant TB it really is essential that they are provided with treatment. This is not only for their sake, and it may indeed save their lives. It is also because once people are taking treatment they stop being infectious, and can no longer spread drug resistant TB to other people.
For MDR-TB the median cost per patient treated was US$9,529 in 2016. New shortened regimens of 9-12 months cost about US$1,000 per person.
There are 30 “high burden” countries for MDR-TB. The list of high burden countries was revised in 2016.
The tables below show the estimated number of cases for each “high burden” country. But these are only the estimates for the number of cases of MDR-TB among those cases of pulmonary TB notified to WHO. There will in addition have been many cases of MDR-TB among those cases of TB which were either not detected and/or not notified.
|Country||Estimated % of new cases with MDR-TB or RR-TB||Estimated % of previously treated cases with MDR-TB or RR-TB||Incidence of MDR-TB or RR-TB||% of MDR among MDR-TB or RR-TB cases|
|Papua New Guinea||3.4||26||1,900||78|
|Republic of Moldova||26||56||2,300||97|
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WHO treatment guidelines for drug resistant tuberculosis 2016 update http://apps.who.int/iris/handle/10665/250125/
Global Tuberculosis Control 2017, WHO, Geneva, 2017 www.who.int/tb/publications/global_report/en/
Multidrug-resistant Tuberculosis (MDR-TB) 2016 update, WHO, Geneva, 2016 www.who.int/tb/publications/factsheets/en/
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|1.||↑||Dodd,P “Global burden of drug-resistant tuberculosis in children: a mathematical modelling study”, the Lancet, 2016, www.thelancet.com/journals/laninf/article/PIIS1473-3099(16)30132-3/abstract|