Smear campaign: Faster detection of multidrug-resistant TB for public health

There is a new tool in the arsenal to fight multidrug-resistant tuberculosis (MDR-TB): a rapid diagnostic test that can function in high-burden settings such as public health clinics. MDR-TB is increasingly on the rise, and spreads most rapidly through vulnerable communities that are already riven by HIV and poverty. One of the biggest barriers to appropriate treatment is the lengthy diagnostic process of conventional techniques that is not well-suited to public health settings serving vulnerable populations.

“With continued delay of testing results, and thus, treatment, the patient will likely transmit the infection to those persons they come in close contact with,” said Richard O’Brien, M.D., senior investigator from the Foundation for Innovative New Diagnostics, a nonprofit funded in part by USAID and the Bill & Melinda Gates Foundation, which sponsored the study. “TB is already the leading cause of death among AIDS patients worldwide. This association is particularly lethal when drug-resistant TB is being transmitted. MDR-TB, with resistance to the most important anti-TB drugs, isoniazid and rifampicin, is even more lethal.”

The study is reported in first issue for April of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society. Dr. O’Brien and his colleagues found that using a molecular assay test, as opposed to conventional culture techniques, may revolutionize the diagnosis and reporting of MDR-TB in these high-infection areas by delivering the critical results more quickly, and perhaps even more accurately—thus enabling proper treatment to begin promptly.

The study took place in a national health laboratory in Cape Town, South Africa, which serves over 4.2 million people and processes about 400,000 specimens annually. The testing was performed on residual portions of specimens originally collected for other purposes. They were able to obtain interpretable results within 1-2 days in 97 percent of smear-positive samples, and had a better than 98 percent specificity and sensitivity rate for multidrug resistance.