The Truenat MTB and MTB Plus assays use chip-based real-time micro PCR for the semiquantitative detection of MTBC directly from sputum specimens and can report results in under an hour. The assays use automated, battery-operated devices to extract, amplify and detect specific genomic DNA loci.
The assays are designed to be operated in peripheral laboratories with minimal infrastructure and minimally trained technicians, although micropipetting skills are required. A practical guide is available to assist implementers considering these tests (13).¹⁰
If a positive result is obtained with the MTB or MTB Plus assay, an aliquot of extracted DNA is run on the Truenat MTB-RIF Dx assay to detect mutations associated with RIF resistance. WHO recommends using Truenat MTB, MTB Plus and MTB-RIF Dx tests in the following situations (5):¹¹
- In adults and children with signs and symptoms of pulmonary TB, the Truenat MTB or MTB Plus may be used as an initial diagnostic test for TB rather than smear microscopy or culture.
- In adults and children with signs and symptoms of pulmonary TB and a Truenat MTB or MTB Plus positive result, Truenat MTB-RIF Dx may be used as an initial test for RIF resistance rather than culture and phenotypic DST.
- These recommendations apply to the use of the test with sputum specimens from people living with HIV/AIDS (PLHIV), based on extrapolation of the data on test performance with smear-negative sputum specimens; and
- These recommendations apply to the use of the test with sputum specimens from children, based on extrapolation of the data from adults, although the test is expected to be less sensitive in children.
¹⁰ See http://stoptb.org/assets/documents/resources/publications/sd/Truenat_Implementation_Guide.pdf
¹¹ See https://apps.who.int/iris/bitstream/handle/10665/342331/9789240029415-eng.pdf