Defining MDR- and XDR-TB

Multidrug-resistant tuberculosis (MDR-TB) is defined as TB that is resistant to both isoniazid [INH] and rifampicin [RMP], two of the first-line drugs used in treating smear-positive pulmonary tuberculosis.

Extensively drug-resistant tuberculosis (XDR-TB) is defined by the WHO as MDR-TB with additional resistance to any fluoroquinolone (FQ) and to at least one of three injectable second-line anti-tuberculosis drugs used in treatment (capreomycin [CPM], kanamycin [KM] or amikacin [AMK]).

 

Some 440,000 cases of multidrug-resistant tuberculosis (MDR-TB) are identified each year, causing at least 150,000 deaths from a disease that should be curable. Extensively drug-resistant TB, which has an even higher fatality rate, has now been reported in more than 65 countries.

 

Drug-resistant TB is the end result of a number of different failures, each of which, on its own, is solvable with existing tools. The Union offers technical assistance in MDR-TB in the field to more than 15 countries yearly and has developed a package, including this technical assistance, training and research to support countries in implementing and developing an MDR-TB project. To address all of the issues and stop the spread of this disease requires a comprehensive, multi-pronged strategy, such as The Union has developed.

When TB is misdiagnosed or the treatment is poorly managed, the doors open to drug resistance.

Consequently training for people at every level of the health care system is central to The Union's approach. More than 300 people including physicians from 35 countries participated in MDR-TB training offered by The Union in 2010. These international and national courses in English, French or Spanish train clinicians to manage MDR-TB cases and cover questions ranging from logistics and procurement to ethics and human rights.

Patients who do not correctly take the medicines required to complete their TB treatment are at high risk for developing drug-resistant tuberculosis and passing on these new strains.

Strong programmes for case detection, diagnosis and patient monitoring are all critical to avoid this scenario. At the request of an NTP, The Union helps review plans, procedures, policies and systems and makes suggestions for improvement. In recognition of the pivotal role of laboratories in diagnosing and monitoring drug-resistant strains of the disease, The Union has also helped develop an international network of TB reference laboratories.

Use of poor quality medicines and drug shortages are also leading causes of drug-resistant TB.

If the quality of first-line TB drugs is not assured – or the supply is not adequate to meet the needs of those in treatment – patients will not be cured and may develop MDR-TB. They will then require treatment with the more expensive second-line drugs (SLD). The Union works closely with NTPs to support them in the implementation of best practices for ordering, storing and distributing medicines, as well as to assure the quality of the medicines selected for national procurement and to monitor their quality.

Treating drug-resistant TB is much more expensive and can take up to two years – creating a strain on both patients and health systems.

Through its operational research and clinical trials programmes, The Union continually seeks new solutions to issues of prevention, treatment and control. The Union also collaborates with international working groups, such as the Green Light Committee, and publishes recommendations on these issues.