A study published yesterday by the Lancet has found much higher rates of drug resistant TB than previously estimated in eight countries around the world. The study found that among patients with multi-drug resistant TB (MDR-TB), 43 percent of cases were resistant to at least one second-line drug used to treat MDR-TB.

TB patients are treated with a six to nine month course of treatment that costs as little as $20 in the developing world. However, if drugs are taken incorrectly or stopped prematurely, the TB bacteria can re-emerge and become resistant to medication. Drug resistant strains are much more costly and difficult –sometimes even impossible – to cure. Drug resistant TB strains often develop in areas where case management is weak and where there is poor TB control.

MDR-TB is a drug resistant form of TB that does not respond to the standard treatment using first-line drugs. Extensively drug-resistant TB (XDR-TB) occurs when resistance to second-line drugs develops on top of MDR-TB.

The Lancet study enrolled 1,278 MDR-TB patients in Estonia, Latvia, Peru, Philippines, Russia, South Africa, South Korea and Thailand and tested them to see how many were resistant to second-line drugs. Among all patients, 43.7 percent were resistant to at least one second-line drug and 6.7 percent had XDR-TB.

Further study analysis found that high risk factors for XDR-TB included previous treatment with second-line drugs, unemployment, a history of imprisonment, alcohol abuse and smoking.

One of the study’s authors, Sven Hoffner from the Swedish Institute for Communicable Disease Control, has warned:

“Most international recommendations for TB control have been developed for MDR TB prevalence of up to around 5%. Yet now we face prevalence up to ten times higher in some places, where almost half of the patients with infectious disease are transmitting MDR strains.”

Drug resistance is entirely man-made and caused by inconsistent or incorrect treatment. New resources and political commitment are desperately needed to control the spread of drug resistant TB.

More news coverage of the Lancet study: