Faster TB test may prevent its spread

A new test that can detect multiple-drug-resistant tuberculosis in two days instead of the standard two to three months promises to help significantly improve treatment and prevent the spread of the airborne infection, the World Health Organization (WHO) said Monday.

Multiple-drug-resistant TB, or MDR-TB, is a growing public-health problem in the world. Five percent of new TB cases are resistant to first-line drugs. That is 450,000 of the 9 million new TB cases that are detected each year, WHO says.

In the United States, the prevalence of drug-resistant tuberculosis among foreign-born TB patients has been about 1.5 percent, roughly three times the percentage among U.S.-born patients with TB.

"The new test is revolutionary," said Dr. Mario Raviglione, WHO's director of tuberculosis control, because "it changes completely the way we will be dealing with MDR-TB."

Detecting cases rapidly and accurately is a major source of delay in tuberculosis control. In most developing countries, cases cannot be detected easily or at all, leading to lags in starting proper treatment that can lead to a patient's death and the further spread of resistant strains.

The TB test, called a line probe assay, costs less than $8 and detects mutations in bacterial DNA linked to drug resistance.

It is based on the same laboratory methods that scientists have used to determine parentage and detect certain genetic diseases, said Dr. Richard O'Brien, an official of the Foundation for Innovative New Diagnostics (FIND).

WHO, a U.N. agency, estimates that worldwide only 2 percent of drug-resistant cases are now being detected and treated appropriately.

Drug-resistant TB, like drug-sensitive TB, can be transmitted by an infected individual in droplets through coughing, sneezing, singing and other activities.

It may require two years of treatment with drugs that are much more costly than the first-line regimen. Technically difficult surgery may also be required.

Health officials have sounded alarms because they believe TB could reach the point where most new cases in some countries are resistant to many drugs without efforts like the new lab test to help stop the spread of the disease.