Evaluating diagnostic performance of Truenat MTB Plus for gastrointestinal tuberculosis

Prompt and accurate diagnosis of gastrointestinal tuberculosis (GITB) along with simultaneous detection of drug resistance is inevitable for tuberculosis elimination. Truenat MTB Plus (TruPlus), a chip-based real-time polymerase chain reaction assay, was evaluated for the first time for diagnosing GITB and detecting rifampicin resistance.

Fifty ileocecal biopsy specimens (5 microbiologically confirmed GITB [culture-positive], 25 clinically confirmed GITB [culture-negative], and 20 control patients) processed in the Department of Microbiology between 2011 and 2021 were subjected to TruPlus assay, Xpert MTB RIF assay multiplex polymerase chain reaction. Their performance was evaluated against both culture and composite reference standard.

The overall sensitivity and specificity of TruPlus in diagnosing GITB was 70% (21/30) and 100%, respectively. The sensitivity was 60% (3/5) for microbiologically confirmed cases and 72% (18/25) for clinically confirmed cases. Performance of TruPlus was superior to Xpert (sensitivity = 30%; P = 0.001) and comparable with MPCR (sensitivity = 83.33%; P = 0.13). Both TruPlus and MPCR had moderate agreement with reference standards, and MPCR detected additional three cases. Both TruPlus and Xpert correctly reported Rifampicin resistance in three cases.

TruPlus, with its greater portability and higher sensitivity than Xpert, could serve as an important tool for diagnosing GITB and rifampicin resistance at outreach endemic areas.