'Exclusively drug-resistant tuberculosis' or XDR-TB is a menacing public health problem that is even deadlier and more common than suspected. XDR-TB patients are four times as likely to fail treatment and three times more likely to die than patients with other forms of multi-drug-resistant tuberculosis (MDR-TB), according to a recent study. Researchers directly compared XDR-TB patients with those having MDR-TB to determine the differences in treatment outcomes and long-term survival rates. Researchers also found that MDR-TB was "a major threat to public health," representing 2.7 percent of new TB cases in South Korea in 2004, up from 1.6 percent in 1994. Since its public appearance in 2006, XDR-TB rekindled an urgent interest in preventing, fighting and containing TB. But little was known about how this variant changed the face of combating TB on all fronts. "Treatment outcomes [of XDR-TB] have varied among studies, and data on long-term survival are still scarce," wrote Tae Sun Shim, an associate professor at Asan Medical Centre, Seoul, South Korea, and a principal investigator of the study. This "is the largest report that we know of that compares patients with XDR-TB with other patients with MDR-TB to determine the impact of XDR-TB on treatment outcomes and long-term survival in mostly HIV-negative patients with MDR-TB." The study reviewed the medical records of more than 1,400 patients in South Korea with MDR-TB (which includes XDR-TB) from all national hospitals, Korean National TB Association chest clinics and select university hospitals. Researchers found that patients with XDR-TB were significantly older than MDR-TB patients, were more likely to have a history of treatment with second-line TB drugs, and more likely to have a history of being treated for TB two or more times. Perhaps the biggest public health threat associated with XDR-TB, however, is not its virulence, but the lack of information and treatment options that medical authorities have on which to draw, according to a release of the American Thoracic Society. The collective dearth of knowledge was likened by Giovanni Battista Migliori, Morgan Richardson and Christopher Lange, co-authors of the accompanying editorial, to the proverbial blind men trying to describe an elephant - too big a task to accomplish with too little information. The results were published in a November issue of the American Journal of Respiratory and Critical Care Medicine.