Evaluation of Truenat MTB/RIF Test in Comparison with Microscopy and Culture for Diagnosis of Extrapulmonary Tuberculosis in a Tertiary Care Centre

Abstract

Introduction: Worldwide, Extrapulmonary Tuberculosis (EPTB) accounts for 15-20% of all cases of TB. The diagnosis of EPTB is a big challenge, as the number of Mycobacterium tuberculosis(MTB) bacilli in the tissues and other organs is often very low. Truenat MTB/RIF (rifampicin) is a novel method, which is battery operated, point-of-care and chip-based Real Time Polymerase Chain Reaction (RT-PCR) micro device. Aim: To evaluate Truenat as a screening test in the diagnosis of EPTB in comparison with microscopy and culture. Materials and Methods: A prospective cross-sectional study was carried out over a year in which samples from suspected cases of EPTB fitting in the inclusion criteria were subjected to Ziehl-Neelsen (ZN) staining for smear microscopy, culture on Lowenstein Jensen (LJ) medium and PCR for MTB by Truenat. Comparisons were made between the tests and the data was presented using summary statistics with 95% Confidence Interval (CI). Results: A total of 248 samples were received from suspected cases of EPTB. Out of the different samples tested, 9 (3.6%) were positive with Truenat MTB. The predominant type of EPTB observed in the study was lymph node Tuberculosis (TB) (66.6%) followed by intestinal, pleural and skeletal TB. Out of the 106 samples tested for culture, four were culture positive for MTB and out of 178 samples tested for microscopy, three were positive for acid fast bacilli. Sensitivity, specificity, Negative Predictive Value (NPV), Positive Predictive Value (PPV), observed agreement of Truenat with culture and microscopy were 100%, 95.1%, 100%, 44.4%, 95.3% and 100%, 96.6%, 100%, 33.3%, 96.6%, respectively. Conclusion: Truenat MTB test is a cost-effective rapid molecular test with good sensitivity and specificity for the diagnosis of EPTB in low resource settings.