Assessing the utility of Truenat in extrapulmonary tuberculosis diagnosis – A NRL’s experience

Background Diagnosis of extra pulmonary TB (EPTB) remains a big challenge. While data on utility of Xpert testing in EPTB diagnosis is enormous, there is limited data on Truenat MTB testing. Aim In this study we aimed to evaluate the usefulness of Truenat in EPTB diagnosis. Materials and methods The study included patients suspected and/or treated for EPTB located from Chennai district during the year 2021–2022. All processed EPTB samples were subjected to smear microscopy, culture and Truenat MTB testing. Results Of the 195 samples tested, 38 (19.4%) samples were positive for EPTB by any one of the diagnostic methods (smear, culture, microscopy). Out of these 38, 16 (42.1 %) were positive for MTB by Truenat and negative by Culture, 12 (31.5%) were positive by culture but negative by Truenat and 8 (21%) were positive by both Truenat and/or smear and culture. The sensitivity and specificity of the test was calculated with the composite reference standard (Culture (exclusion of colonies as positives), clinical conditions, and smear) and was found to be 60% and 100% respectively. Conclusion Truenat MTB test is a cost-effective rapid molecular test that can be used only for the diagnosis of presumptive EPTB and not on follow-up samples.