Diagnostic accuracy of truenat MTB plus for the detection of pulmonary and extrapulmonary tuberculosis

Background

The diagnosis of Tuberculosis (TB) has been a challenge till the advent of rapid molecular diagnostic tests. The traditional diagnostic tests have its own limitations with regard to its performance or the turnaround time. Truenat MTB Plus assay, a battery-operated molecular assay developed in India has been introduced for its use in pulmonary TB (PTB). However, the diagnostic accuracy of the assay is not well studied in comparison with Mycobacterial culture, especially for extrapulmonary TB (EPTB).

Aim

We aimed at evaluating the diagnostic accuracy of Truenat MTB Plus assay for both PTB and EPTB comparing with culture for adult population.

Methods

The specimens from presumptive PTB and EPTB patients were processed for Truenat MTB Plus assay, solid or liquid culture and AFB staining. The electronic data of all the specimen reports collected retrospectively were analysed for the sensitivity and specificity.

Results

Out of the 736 samples which had valid culture reports, 364 (49.4 %) were respiratory and 372 (50.6 %) were extrapulmonary specimens. The test positivity rate for smear microscopy, Truenat MTB Plus assay and culture was 3.7 % (27), 8.2 % (60), 7.1 % (52) respectively. Of the 60 Truenat MTB Plus positive patients with TB, 33 (55 %) were PTB and 27 (45 %) were EPTB. We estimated overall sensitivity and specificity of Truenat MTB Plus as 90 % (95 % CI: 73.4–97.8) and 98. 2 (95 % CI:96–99.3) respectively for the detection of PTB. The overall sensitivity and specificity for EPTB was 81.8 % (95 % CI: 59.7–94.8) and 97.4 % (95 % CI: 95.1–98.8) respectively.

Conclusions

Truenat MTB Plus assay has comparable diagnostic accuracy with other molecular assays. The Truenat MTB Plus assay can be used for the diagnosis of PTB and EPTB, especially in resource limited settings.