MDR-TB is an abbreviation of Multi Drug Resistant 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 won’t work. Other drugs then need to be taken by the person if they are to be cured of TB.
For many years MDR-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, which also detects resistance to rifampicin.
People with RR-TB are resistant to rifampicin, with or without resistance to other drugs. MDR/RR-TB means patients with MDR-TB as well as patients with TB resistant to rifampicin.
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 have primary TB.
Globally in 2015 there were about 480,000 people estimated to have become ill with MDR-TB. In addition there were an estimated additional 100,000 people who had rifampicin TB (RR-TB). So the total number of people estimated to have had MDR-TB or RR-TB was 580,000 in 2015 .
MDR-TB accounts for about 3.3% of new TB cases. Also, about 3.9% of new, and about 21% of previously treated TB cases were estimated to have either rifampicin or multi drug resistant TB in 2015.
About 9.5% of MDR-TB cases in 2015 had additional drug resistance, which means that they may have what is known as extensively drug resistant TB (XDR).
In 2015 MDR-TB and RR-TB caused approximately 250,000 deaths.
There is a large difference between the number of patients estimated to have had MDR-TB or RR-TB (580,000), and the number of people actually reported (notified) to WHO (132,000). In 2015 only 30% of the TB patients notified globally to WHO were tested for MDR-TB or RR-TB, although this was an improvement on the 22% tested in 2014. The notification numbers among different WHO regions for 2015 are shown in the table below.
|Region||Total notified||MDR-TB & RR-TB cases notified|
A total of 125,000 patients were enrolled on MDR-TB treatment in 2015 (up from 111,000 cases in 2014). However, this represents only about 22% of the estimated incident MDR/RR-TB cases in 2015. The gap between detected MDR/RR-TB cases and enrollments on treatment does though appear to have narrowed over time.
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 being 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 World Health Organisation 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.
Only 52% of the MDR-TB or RR-TB patients who started treatment in 2013 were successfully treated. 17% of the patients died and in 9% of the patients their treatment failed. 22% were lost to follow up or not evaluated.
There are 30 “high burden” countries for MDR-TB. The list of high burden MDR-TB 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||38|
|Republic of Moldova||32||69||3,900||79|
WHO treatment guidelines for drug resistant tuberculosis 2016 update http://apps.who.int/iris/handle/10665/250125/
Global Tuberculosis Control 2016, WHO, Geneva, 2016 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/