Slow progress in diagnosis and treatment of MDR-TB and XDR-TB

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There were in excess of 500,000 cases of multidrug-resistant tuberculosis (MDR-TB) in 2007, according to figures released in the World Health Organization 2009 Global Tuberculosis Control report. But, says WHO, less than 30,000 cases of MDR-TB were notified in 2007, and just 1% of the global population of MDR-TB cases received appropriate treatment.

Cure rates for the infection varied enormously between countries. Although 73% of patients with MDR-TB were cured in the Philippines, the figure for Romania was only 38%, where a large proportion of patients either died or experienced treatment failure.

A ministerial level meeting will be held in Beijing in April, where representatives of the 27 countries with the highest burden of drug-resistant TB will discuss ways of improving the diagnosis and treatment of MDR-TB and extensively drug-resistant TB (XDR-TB), strains of the infection that have resistance to key second-line drugs.

Glossary

multidrug-resistant tuberculosis (MDR-TB)

A specific form of drug-resistant TB, due to bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. MDR-TB usually occurs when treatment is interrupted, thus allowing organisms in which mutations for drug resistance have occurred to proliferate.

extensively drug-resistant TB (XDR-TB)

A form of drug-resistant tuberculosis in which bacteria are resistant to isoniazid and rifampicin, the two most powerful anti-TB drugs, plus any fluoroquinolone and at least one injectable second-line drug. 

second-line treatment

The second preferred therapy for a particular condition, used after first-line treatment fails or if a person cannot tolerate first-line drugs.

treatment failure

Inability of a medical therapy to achieve the desired results. 

loss to follow up

In a research study, participants who drop out before the end of the study. In routine clinical care, patients who do not attend medical appointments and who cannot be contacted.

Cases of MDR-TB were concentrated in a small number of countries, with 27 accounting for 85% of all cases, with 15 high-prevalence countries concentrated in Eastern Europe. In Russia, 20% of all TB cases involved MDR-TB.

By late 2008, 55 countries had reported cases of XDR-TB, including five that experienced their first case of the infection in 2007.

Only 220,000 tests were performed worldwide to determine the susceptibility of any TB case to anti-TB drugs. These tests found just under 30,000 cases of MDR-TB, with 54% of the identified cases being in Europe. Drug susceptibility test results were reported for only 6% of all global cases of TB and an estimated 9% of cases of MDR-TB.

A programme called the Green Light Committee was established in 2000 with the purpose of increasing access of appropriate second-line TB therapy for patients with MDR-TB. Below 1% of all patients with MDR-TB received treatment from a Green Light Committee-approved project in 2007. The authors comment, “outside Green Light Committee-approved projects, it is not known how many notified cases are enrolled on treatment, and of these how many received treatment in line with WHO guidelines”.

As treatment for MDR-TB takes between 18 and 24 months, outcome data in the report was for individuals who started treatment in 2004. The authors restricted their comments to patient cohorts of at least 100. The highest success rates were seen in Green Light Committee-approved projects in the Philippines (73%) and Latvia (71%). Favourable treatment outcomes were seen amongst 61% of MDR-TB patients in the USA and between 53% and 58% in Green Light Committee-approved projects in Peru and Russia.

Outcomes were notably poorer in two countries without Green Flag Committee projects, with 62% of MDR-TB patients in Romania experiencing treatment failure or dying, whereas in Morocco an estimated 50% of patients were lost to follow-up and only 255 had a successful outcome.

The Global Plan to Stop TB recommended in 2008 that 100,000 patients with MDR-TB and 10,000 patients with XDR-TB should be enrolled on treatment. These targets are three times greater than what was achieved in 2007 and projections for both 2008 and 2009 are also well below this figure.

“The relatively small number of MDR-TB cases diagnosed and treated to date, the modest projections of the patients to be treated in the future and the fact that only 25% of countries have reported XDR-TB all demonstrate how much work remains to be done to improve the availability and provision of diagnosis and treatment for MDR-TB and XDR-TB”, write the authors. These issues will provide the focus for the meeting of international ministers in Beijing next month.