Multi-centric validation of Truenat MTB Rif Dx for Diagnosis of Extrapulmonary Tuberculosis

Extra-pulmonary TB (EPTB) is difficult to diagnose due to paucibacillary nature of disease. Current study evaluated accuracy of Truenat MTB-Rif Dx (TN), for detection of Mycobacterium tuberculosis and resistance to rifampicin. Samples were collected from 2103 treatment naive adults with presumptive EPTB, and tested by smear microscopy, liquid culture (LC) (MGIT-960) and GeneXpert MTB/RIF (GX) (Microbiological Reference Standards, MRS). TN results were compared to MRS and Composite Reference Standards (CRS, Microbiology, histopathology, radiology, clinical features prompting decision to treat, response to treatment). TN and GX results were further compared to Clinical Reference Standards (CRS). CRS grouped patients into 551 confirmed, 1096 unconfirmed, and 409 as unlikely TB. TN sensitivity and specificity was 73.7% and 90.4% against GX. Against LC, TN sensitivity and specificity was 62.3% and 84.9%; highest sensitivity (89%) in pus samples and specificity (92%) in CSF was similar to GX. TN sensitivity was better in fluid and biopsy samples, slightly inferior for lymph node aspirates. TN sensitivity for RIF resistance detection was slightly superior to GX. TN detected 169 TB patients initiated on treatment, which were missed by GX. The study establishes TN at par with GX and can be utilized for quick and accurate diagnosis of EPTB.