NEW YORK (Reuters Health) – In patients with extensively drug-resistant tuberculosis (XDR TB), adding a later-generation fluoroquinolone to the treatment regimen may improve outcomes, even when drug-susceptibility testing shows resistance to a representative fluoroquinolone, a new meat-analysis shows.
XDR TB refers to cases that are resistant not only to isoniazid and rifampin but also to a fluoroquinolone and at least one of the second-line injectable agents (amikacin, capreomycin, and kanamycin). First described in 2006, XDR TB has now spread to 6 continents and 55 countries, the study team notes in their report, published online May 26th in Clinical Infectious Diseases.
Nearly half a million new multidrug-resistant TB (MDR TB) cases are diagnosed annually, with 1 in 10 thought to be XDR TB.
Not surprisingly, treatment outcomes have been significantly worse for patients with XDR TB. To identify approaches associated with favorable outcomes, Boston-based researchers led by Dr. Karen R. Jacobson at Massachusetts General Hospital reviewed 13 observational studies conducted through May 2009.
Out of the 560 XDR TB patients in the studies, only 43.7% had favorable outcomes, defined as cure or treatment completion — “well below the 62% to 70% reported for patients with MDR TB,” the researchers note. Nearly 21% of the XDR TB study patients died.
Clearly, Dr. Jacobson told Reuters Health by e-mail, treatment outcomes for XDR TB “are still quite poor and worse than for patients infected with MDR TB or drug sensitive TB.”
It is noteworthy, she said, that studies in which a higher proportion of patients received a later-generation fluoroquinolone reported a significantly higher proportion of favorable outcomes (p = 0.02).
“We found that a cohort in which all patients received later-generation fluoroquinolones would have a 40% increase in favorable outcomes, compared with a cohort in which no patients received later-generation fluoroquinolones,” the researchers wrote.