QUICK & ACCURATE: It used to take months to determine if a person had tuberculosis. But waiting for test results could be deadly, especially with drug-resistant TB spreading rapidly. Now, according to the World Health Organization, there's a new test that makes the diagnosis in just days. It plans to roll out the test, called a line-probe assay, in four African countries this year.

Currently, labs have to wait up to three months to see if saliva incubated in dishes could be treated with tuberculosis (TB) drugs. The new approach looks at DNA for genetic mutations and tests the drugs against the mutations. This shortens the diagnostic time. Hopefully, this will help in the efforts to control the spread of TB, particularly in Africa and other nations with AIDS epidemics—TB mortality is highest in HIV-positive people.

New Test Targets Drug-resistant TB

TB spreads in water droplets, usually through sneezing, coughing, spitting or singing. Although it's treatable, mutated strains of TB are now resistant to drugs.

Called multidrug-resistant TB (MDRTB), these strains make up 5% of the 9 million TB cases diagnosed each year. And MDRTB, which is harder to treat than regular TB, is on the rise.

If the drug-resistant strain of TB gets a solid hold on a person's body, it can take up to two years to cure—and only with expensive new drugs. Only 2% of people with MDRTB are diagnosed and treated.

Part of the challenge is the length of the time it takes to make a TB diagnosis. While waiting for results from the traditional three-month test, a person with regular TB...

• gets sicker
• spreads the illness to others
• risks having the TB mutate into an MRTRB strain, making treatment harder

Doctors anticipate that with the new test, the number of people diagnosed with MDRTB and treated will increase to 15%. They urge that the new test be applied everywhere, but especially in poor countries with a lot of AIDS cases—HIV makes a person more susceptible to TB.

Without an accurate diagnosis of MDRTB, doctors might prescribe the wrong antibiotics. This can lead to extensive drug-resistant TB-XDRTB—which is untreatable and already found in 49 countries (including the United States).

New TB Test Quick, WHO Says Cost of Using Worldwide Unknown

The new TB test is relatively simple—at least for the patient:

1. Medical technicians collect bacteria-containing saliva from people who are at risk for TB.
2. Lab technicians extract DNA from the saliva.
3. They use amplifying techniques to make sufficient copies of the DNA.
4. They look for bacterial genetic mutations that lead to resistance of the two most effective TB drugs, isoniazid and rifampin.

Medical and lab technicians have to learn how to administer the test properly, or they risk ...

• catching TB if they don't use the proper techniques
• contaminating the specimen, leading to invalid test results

Luckily...

• inexperienced technicians can learn how to run the test in less than a week
• well-equipped labs in even the poorest countries can run the tests

Since the test's complexity requires special training for technicians and special lab equipment, forecasting the actual costs is difficult at this time.

"The problems with the test are that they are very, very complex," said Dr. Tido von Schoen-Angerer of Medecins Sans Frontieres (Doctors Without Borders). "The desperate search for much simpler tests has to continue, but this at least is a good step forward in cutting down the time to diagnosis." (Associated Press, 7/1/08)

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Question for Readers:

Do you think the current use of antibiotics has contributed to drug-resistant strains of tuberculosis?