Colour Plate Microcolony Detection of Mycobacterium Tuberculosis in Extra Pulmonary Tuberculosis

Abstract Introduction: Accurate and timely tuberculosis diagnosis is the primary step for initiating effective treatment. The colour plate agar-based culture test (TB-CX test) is a low cost, simple to use, detects Mycobacterium tuberculosis faster. The study conducted to compare the diagnostic accuracy and time to detection of positive cultures using colour test and Lowenstein Jensen culture in extrapulmonary samples. Method: Prospective, laboratory-based study, was conducted on 210 consecutive Extra pulmonary samples received for a period of 18 months in a tertiary care hospital and were directly processed for culture on LJ media and Colour TB CX test along with the microscopy. Result: From 200 samples, 15 were found positive by both methods, 5 were positive on LJ and negative on the colour TB-CX test. The overall sensitivity and specificity of colour TB-CX test compared with conventional LJ culture were, respectively 75% and 100%. The positive predictive value and negative predictive value of colour TB-CX test were 100% and 95.45% respectively as compared to LJ culture. Among the samples Pus showed highest positivity on both LJ media and Colour plate. In addition, 35% of positive samples were detected within the first three weeks on colour TB-CX plate agar, and 5% on LJ. The minimum time for detection was 16 days for colour TB-CX test and 27 days for LJ media. Conclusion: The colour plate test allows early detection of MTB diagnosis in a median time of 23 days. This rapid method could be used for the diagnosis of Mycobacterium tuberculosis in EPTB.