Abstract

Rifampin resistance is a good marker for multidrug-resistant tuberculosis ( MDR-TB). Therefore, determining of resistance as soon as possible will provide the clinician to make modifications on therapeutic protocols of the patients stayed unresponsive to the standart regimens. Culture based susceptibility tests which are available in routine use, result in approximately 3 to 4 weeks. In this study, in order to shorten this duration, the specifity and the sensitivity of Fastplaque TB-RIF test based on mycobacteriophages compared with that of Löwenstein Jensen by the proportion method. A total number of 32 strains were used; 21 of them were rifampin resistant while the other 11 were sensitive according to the proportion method. Rifampin- sensitive ATCC 35825 Mycobacterium tuberculosis and rifampin-resistant ATCC 35838 M. tuberculosis were the standart strains of the study. Of these 21 resistant strains, 17 were found to be resistant by the Fastplaque TB-RIF test also, while the other 4 remained sensitive by this test. On the other hand, 9 of the 11 sensitive strains according to the proportion method, showed the same sensitivity pattern, but 2 of them were found to be RIF-resistant by this technique. As a result, the sensitivity of this test was found to be 80%, specificity 81%, negative predictive value 69% and positive predictive value 89% compared with the proportion method. No statistical difference was observed between two tests with Mc Nemar test (p=0.687). Therefore, positive results obtained in 48 hours by this test may help early diagnosis of the MDR-TB cases.