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Cases of multidrug-resistant tuberculosis (MDR-TB) hit an all-time high worldwide in 2009 and 2010, with 1 country reporting multidrug resistance in 65.1% of all previously treated TB cases, according to the latest World Health Organization (WHO) study, published in the February Bulletin of the World Health Organization.
Matteo Zignol, MD, MPH, from the Stop TB Department, WHO, Geneva, Switzerland, and colleagues analyzed data collected from 2007 to 2010 from 80 countries and 8 territories. The analysis showed that Eastern Europe and central Asia continue to record the world's highest proportion of MDR-TB. Still, there are no data on drug-resistant TB from much of Russia, India, and Africa, and from large portions of Eastern Europe and central Asia, the authors report.
"Surveillance of resistance to drugs is the cornerstone of TB control," Dr. Zignol said in a news release. "Following 15 years of intensive effort, we now have high quality data for two-thirds of countries in the world. At the same time, we don't know the full extent of the problem because we lack data from many countries, in particular India and most of Africa where the TB burden is high."
One bright spot in new surveillance efforts, the authors points out, is China, which conducted its first nationwide survey in 2007. Dr. Zignol and colleagues call China's efforts "a critical step towards addressing MDR-TB in one of the largest TB control programmes in the world." China, India, and Russia are home to more than half of the world's MDR-TB cases, the report states.
Worldwide, 3.4% (95% confidence interval [CI], 1.9% - 5.0%) of all new TB cases are multidrug-resistant, meaning Mycobacterium tuberculosis resists treatment with at least rifampicin and isoniazid. Among previously treated TB cases worldwide, 19.8% (95% CI, 14.4% - 25.1%) of TB cases are multidrug resistant, according to the report.
Some MDR-TB cases are considered extensively drug resistant (XDR), meaning they not only meet the criteria for multidrug resistance but also fail to respond adequately to fluoroquinolone and at least 1 second-line injectable agent, such as amikacin, kanamycin, or capreomycin. Worldwide, some 9.4% (95% CI, 7.4% - 11.6%) of MDR-TB cases are XDR cases. The number of MDR-TB cases considered to be XDR cases rose to more than 10% in South Africa (10.5%) and 3 former Soviet Union countries: Estonia (19.7%), Latvia (15.1%), and Tajikistan (Dushanbe city and Rudaki district, 21.0%).
However, only 38 countries and 3 territories reported surveillance data for XDR-TB. Among those, only 6 had more than 10 cases of XDR.
The Russian oblast of Murmansk, on the Kola Peninsula near Finland, had the highest level of newly diagnosed MDR-TB, at 28.9%. The Republic of Moldova, a landlocked country between Ukraine and Romania, had the highest rate of MDR-TB among previously treated TB cases, at 65.1%.
TB cases resistant to several treatment regimens require longer and more treatment regimens and are less likely to be cured. Despite the rising number of resistant cases, in 2010, only 16% of the world's patients with MDR-TB received appropriate treatment, the WHO report reveals.
In the United States, MDR-TB cases are in decline, falling even more quickly than new TB cases, the authors report. US TB cases have dropped 5.1% per year since 1996, and MDR-TB diagnoses declined 5.4% per year in the same period. Surveillance showed that 1.1% of new TB cases diagnosed in the United States were multidrug resistant in 2010, and 4.4% of previously treated cases were multidrug resistant.
Despite high MDR-TB rates in Latvia and Estonia, both those countries, along with the United States, have seen a decline in new TB cases and in MDR-TB cases during the last decade.
MDR-TB is increasing most rapidly in Botswana, at 10.9% per year; Peru, at 19.4% per year; and the Republic of Korea, with an increase of 4.3% per year. The Republic of Korea is also recording a 7.4% annual increase in new TB cases. Despite increases in MDR-TB rates, Botswana's overall new case rate is nearly stable, increasing at 0.3% per year, and Peru's rate of new cases is declining by 3.3% per year.
WHO began gathering drug resistance data from 127 countries in 1994 with the launch of the Global Project on Anti-tuberculosis Drug Resistance Surveillance. Today, 64 countries have continuous surveillance based on routine susceptibly testing of all patients with TB. The rest of the countries rely on special surveys of representative patient samples.
Among the report's other findings:
  • Countries with new cases of MDR-TB at more than 12% include Belarus, at 25.7%; Estonia, at 18.3%; several oblasts of the Russian Federation, with Murmansk having the highest at 28.9%; and Tajikistan, with Dushanbe city and Rudaki district at 16.5%.
  • Countries with MDR-TB in previously treated cases above 50% included Belarus, at 60.2%; Lithuania, at 51.5%; the Republic of Moldova, at 65.1%, 5 oblasts of the Russian Federation; and Tajikistan (Dushanbe city and Rudaki district), at 61.6%.
  • Patients with TB who have HIV were no more likely to have a drug-resistant form of TB than those without HIV. In the 17 countries and 1 territory that looked at HIV status, odds of having MDR-TB among HIV-positive cases was 40% higher than among those without HIV (pooled odds ratio [OR], 1.4; 95% CI, 0.7 - 3.0; OR consistent across countries, I2 = 23.2%; P = .19), but the difference was not significant.
  • The sex of the patients with TB was not a factor in resistance. Among the 58 countries and 2 special territories that collected data on the sex of patients with MDR-TB, odds of MDR-TB were 10% higher among women (OR, 1.1; 95% CI, 0.8 - 1.4; OR heterogeneous across countries, I2 = 32.9%; P = .009), which is not statistically significant.


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