Two quick TB tests compared: accuracy versus cost for real-world use

Tuberculosis remains a persistent global health problem that depends on fast, reliable diagnosis to get people on the right treatment. To help guide where different molecular tests should be used, Zeeshan Sidiq led a study in New Delhi that directly compared two WHO-endorsed nucleic acid amplification tests: Truenat MTB Plus and Xpert MTB/RIF Ultra. The team enrolled 664 people with suspected pulmonary TB at the New Delhi Tuberculosis Centre. Every patient provided paired sputum specimens so both platforms could be run on the same clinical samples. Beyond measuring how well each test found Mycobacterium tuberculosis (MTB) and detected rifampicin resistance (RIF-R), the study also recorded practical operational details such as invalid or indeterminate results and the cost per test. The goal was to assess not just laboratory accuracy but also which test would work better in busy, resource-limited settings — from peripheral clinics to district and reference laboratories — so programs can expand access to molecular testing without compromising quality.

This was a prospective diagnostic accuracy study using Mycobacterial culture as the primary reference standard for MTB detection and phenotypic drug susceptibility testing (pDST) as the reference for RIF-R. Of 664 participants, 98 (14.8%) had culture-confirmed TB and 7 of those 98 (7.1%) had RIF-R. Compared with culture, Xpert MTB/RIF Ultra showed a sensitivity of 97.9% (95% CI: 95.2–100%) and a specificity of 95.5% (95% CI: 93.7–97.3%). Truenat MTB Plus had a sensitivity of 92.5% (95% CI: 85.1–96.6%) and specificity of 90.1% (95% CI: 86.8–92.6%). For rifampicin resistance, Xpert Ultra detected RIF-R with 83.3% sensitivity and 100% specificity, while Truenat MTB-RIF had 75.0% sensitivity and 100% specificity. Operationally, Truenat produced more invalid results (5.9% vs 0%) and far more RIF indeterminate results (46.5% vs 13.2%) than Xpert Ultra. Cost per test differed substantially: approximately INR 800 for Truenat MTB Plus versus INR 1800 for Xpert MTB/RIF Ultra.

The study highlights a clear trade-off between analytical performance and practical deployment. Xpert MTB/RIF Ultra showed superior diagnostic accuracy and far fewer indeterminate or invalid outcomes, which can reduce repeat testing and the need for retreatment decisions based on incomplete results. On the other hand, Truenat MTB Plus and Truenat MTB-RIF offer meaningful cost savings and require minimal infrastructure, making them attractive for peripheral and district-level decentralized testing sites where resources and laboratory capacity are limited. Both platforms markedly outperformed smear microscopy for detecting TB, so either represents an important upgrade from older methods. The authors recommend a tiered diagnostic approach that uses Truenat where decentralization and low cost are priorities and Xpert Ultra at district and reference laboratories where higher throughput and lower indeterminate rates are critical. By leveraging the complementary strengths of both technologies, programs could expand molecular testing access while balancing cost, feasibility, and diagnostic quality to accelerate progress toward TB elimination goals.