Accuracy of the color plate micro-colony detection for the diagnosis of Mycobacterium tuberculosis complex in Northwest Ethiopia

Background: Accurate and timely tuberculosis diagnosis is the primary step for initiating effective treatment. The color plate agar-based culture test (TB-CX test) is low cost, simple to use and detects Mycobacterium tuberculosis faster. Therefore, the main objective of this study was to compare the diagnostic accuracy and time to detection of positive cultures using color test and Lӧwenstein Jensen culture. Methods: A comparative cross-sectional study was conducted at University of Gondar Hospital. A total of 200 sputum samples were collected from TB patients and processed for direct smear microscopy and cultures. Results: Sixty-five percent were found positive on both methods and 4 (2%) were positive on LJ culture and negative on the color plate. The median time for detection of MTB growth was significantly shorter using color plate test (Median 12 days) than LJ culture (Median 21 days) (P < 0.0001). The overall sensitivity and specificity of the color test compared to LJ culture were 97% (95% CI: 93–99) and 100% (95% CI: 94–100), respectively. Conclusions: The color plate test for micro-colonies allows early and accurate MTB diagnosis in a median time of 12 days. This rapid method could be an option for diagnosis of pulmonary TB in resource limited settings.