WHO Recommends 2-Day Test for MDR-TB

The World Health Organization (WHO) now recommends a line-probe assay (LiPA) for the rapid, 2-day detection of multidrug-resistant tuberculosis* (MDR-TB), according to yesterday's press release. LiPA (eg, GenoType MTBDRplus; Hain LifeScience) extracts and amplifies sputum-derived Mycobacterium tuberculosis DNA, which is then hybridized with oligonucleotide probes to detect genes conferring rifampin or isoniazid resistance (eg, rpoB, katG, inhA).

In a 2006 study, the sensitivity and specificity of a rifampin-resistance LiPA (INNO-LiPA.Rif; Innogenetics) or traditional 2-3-month culture were examined in 420 new or retreatment sputum specimens from Asia, Africa, Europe, or Latin America (Studies suggest that rifampin resistance is a reasonable indicator of MDR-TB, where the prevalence of disease is high.) The concordance between LiPA and culture for rifampin resistance was 99.6%.

WHO estimates that only 2% of the world's MDR-TB cases are recognized and treated appropriately, and that the multimillion-dollar initiative to systematically implement LiPA testing in 16 countries will increase that percentage to 15% or higher by 2012. Designated countries will receive the tests and appropriate training through the Stop TB Partnership's Global Drug Facility. According to WHO, Lesotho is ready to implement the use of LiPA for rapid MDR-TB detection, and Ethiopia will be ready by the end of this calendar year.

Photomicrograph of M. tuberculosis in sputum smear stained with Ziehl-Neelson acid-fast stain. Courtesy of CDC/Ronald W. Smithwick.

* Defined as resistance to both rifampin and isoniazid.