Prospective evaluation of thin-layer agar colour test in routine diagnosis of multidrug-resistant TB

BACKGROUND This study evaluated the diagnostic performance of the thin-layer agar MDR/XDR-TB Colour Test (CT), a Mycobacterium tuberculosis complex (MTBC) detection and direct drug susceptibility testing (DST) method with routine sputum, bronchoalveolar lavage and pleural fluid specimen. METHODS In a prospective study, the time and rate of MTBC detection were compared between CT, Löwenstein-Jensen, and MGIT media. Times until DST result, sensitivities, and specificities were evaluated between CT and MGIT 960 indirect DST. RESULTS The cultivation of 177 pulmonary specimens resulted in 83 MTBC-positive cultures. The sensitivity of CT for MTBC detection was 81.3% with a median time of 20 days compared to 13 days and 93.5% for MGIT. The sensitivity of CT for DST results was 100% for isoniazid and levofloxacin and 94.7% for rifampicin. The specificities for isoniazid and rifampicin DST were 97.3% and 98.0% for levofloxacin. The median time until a DST result was significantly shorter with CT than the BACTEC MGIT 960 system, 20 and 27 days, respectively, independent of the specimen type used. CONCLUSIONS The CT is a highly accurate and fast initial diagnostic test for high-incidence settings and could also be used as a first culture and direct DST in peripheral settings. .