Direct detection of Mycobacterium tuberculosis in sputum samples from Guinea Bissau by an rRNA target-amplified test system

Setting. There is a need for more sensitive and rapid methods for laboratory confirmation in the diagnosis of tuberculosis. Objective: To investigate the applicability of a target rRNA amplified test system (AMTDT, Gen-Probe, CA) for rapid detection of Mycobacterium tuberculosis. Design: The rRNA amplified test system was compared to standard methods for acid fast microscopy and mycobacterial culture for the demonstration of M. tuberculosis in sputum samples from 247 patients in Guinea Bissau with suspected tuberculosis. Results: The highest incidence of positive samples was obtained with the AMTDT test. Out of 274 sputum samples 96 (35%) were positive by the AMTDT test, 82 (30%) were positive by culture and 38 (14%) by direct microscopy. Using culture as reference method the sensitivity of the test was 85% (after discrepancy analysis 87%), and the specificity was 86% (after discrepancy analysis 93%). Conclusion: The sensitivity and specificity of the AMTDT test used in this setting indicates that it may be a valuable complement for improving the laboratory diagnosis of tuberculosis.