Clinical and operational value of the XDR-TB definition

¹ WHO Collaborating Centre for TB and Lung Diseases, Fondazione S. Maugeri, Care and Research Institute, Tradate, Italy
² E. Morelli Hospital, Reference Hospital for MDR and HIV TB, Sondalo, Italy
³ National Institute for Infectious Diseases (INMI) L. Spallanzani, Rome, Italy
⁴ University of Tartu, Tartu, Estonia
⁵ Division of Clinical Infectious Diseases, Medical Clinic, Research Centre Borstel, Borstel, Germany
⁶ Fondazione S. Maugeri, Care and Research Institute, Cassano delle Murge, Italy
⁷ University of Perugia, Internal Medicine, Section of Respiratory Diseases, Perugia, Italy
⁸ Supranational Reference Laboratory, S. Raffaele Institute, Milano, Italy
⁹ San Paolo Hospital, University of Milan, Milano, Italy
¹⁰ University of Brescia, Brescia, Italy
¹¹ TB Reference Centre, Villa Marelli Institute, Niguarda Hospital, Milano, Italy
¹² Stop TB Dept, World Health Organization, Geneva, Switzerland

^* To whom correspondence should be addressed. E-mail: gbmigliori{at}fsm.it.

	Abstract

No information is available on the effect of resistance/susceptibility to first-line drugs different from isoniazid and rifampicin in determining the outcome of extensively drug-resistant tuberculosis (XDR-TB) patients, and if being XDR-TB is a more accurate indicator of poor clinical outcome than being resistant to all first-line anti-TB drugs.

To investigate this issue large series of multidrug-resistant (MDR-) and XDR-TB cases diagnosed in Estonia, Germany, Italy and Russian Federation (Archangels Oblast) in the period 1999–2006 were analyzed.

Drug susceptibility testing for first- and second-line anti-TB drugs, quality assurance and treatment delivery was performed according to WHO recommendations in all study sites.

Out of 4,583 culture-positive TB cases analyzed, 361 (7.9%) were MDR and 64 (1.4%) XDR.

XDR-TB cases had a relative risk of 1.58 to have an unfavourable outcome compared with "MDR-TB cases resistant to all first-line drugs" (isoniazid, rifampicin ethambutol, streptomycin and, when tested, pyrazinamide) and a RR of 2.61 compared with "other" MDR-TB cases (those susceptible to at least one first-line anti-TB drug among ethambutol, pyrazinamide and streptomycin, regardless to resistance to the second-line drugs not defining XDR-TB).

The emergence of XDR-TB confirms that problems in TB management are still present in Europe. While waiting for new tools which will facilitate management of XDR-TB, accessibility to quality diagnostic and treatment services should be urgently ensured and adequate public health policies should be rapidly implemented to prevent further development of drug resistance.

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