Advances in Molecular Diagnosis of Tuberculosis

Abstract

Molecular tests for tuberculosis (TB) have the potential to help reach the three million people with TB who are undiagnosed or not reported each year, and to improve the quality of care TB patients receive by providing accurate, quick results, including rapid drug-susceptibility. The World Health Organization (WHO) has recommended the use of molecular nucleic acid amplification tests (NAATs) tests for TB detection instead of smear microscopy, as they are able to detect TB more accurately, particularly in patients with paucibacillary disease and in people living with HIV. Importantly, some of these WHO-endorsed tests can detect Mycobacterial gene mutations associated with anti-TB drug resistance, allowing for tailoring of effective TB treatment. Currently, a wide array of molecular tests for TB detection is being developed and evaluated, and while some are intended for reference laboratory use, others are being aimed at the point-of-care and peripheral healthcare settings. Notably, there is an emergence of molecular tests designed, manufactured, and rolled out in high TB burden countries, some of which are explicitly aimed for near-patient placement. These developments should increase access to molecular TB testing for larger patient populations. With respect to drug susceptibility testing, NAATs and next generation sequencing can provide results substantially faster than traditional phenotypic culture. Here, we review recent advances and developments in molecular tests for detecting TB as well as anti-TB drug resistance.

Learning from COVID-19 to reimagine tuberculosis diagnosis

“…Fifth, we propose exploiting multi-disease molecular technologies. 8 To control COVID-19, countries have needed to scale-up their capacity to run molecular tests. In many settings, this capacity was enabled from pre-existing HIV and tuberculosis programmes that had centralised multi-disease molecular platforms (eg, HIV viral load assays) and could be expanded to meet demand.…”

Targeted next-generation sequencing: a Swiss army knife for mycobacterial diagnostics?

“…A comprehensive overview of the changing diagnostic landscape for mycobacteria is beyond the scope of this editorial [3]. Instead, we will focus on the impact of the adoption of nucleic acid amplification tests (NAATs) [10]. Broadly speaking, these have been developed to accelerate turnaround times and, ideally, combine multiple diagnostic functions (figure 1).…”

“…Moreover, the turnaround time of AST was reduced from weeks to days and even hours compared with phenotypic AST, which is hampered by the slow growth rate of MTBC and the fact that it is typically carried out sequentially (i.e. second-line drugs are only tested when resistance to first-line drugs is found) [5,10]. It should be noted, however, that some compromises were made during the design of these NAATs, which is best illustrated with the Nipro Genoscholar PZA-TB II.…”

“…Another consequence of the goal to maximise the sensitivity of genotypic AST was that only a small number of assays simultaneously identify the most frequent NTM (e.g. the Nipro Genoscholar NTM +MDRTB II [10]). Hence, NTM are typically not differentiated in many settings with limited laboratory capacity, even when they are cultured (i.e.…”

Progress toward Developing Sensitive Non-Sputum-Based Tuberculosis Diagnostic Tests: the Promise of Urine Cell-Free DNA

“…There is an urgent need for accurate, rapid, point-of-care, non-sputum based tests to diagnose TB (5). Over the last ten years, a variety of primarily sputum-based molecular TB diagnostic tests have received World Health Organization (WHO) endorsement and have become commercially available, such as Xpert MTB/RIF (Cepheid, USA), Xpert MTB/RIF Ultra (Ultra) (Cepheid, USA), and Truenat MTB/RIF (Molbio Diagnostics, India) (6). Unique product delivery models have been explored in an attempt to increase access to these new TB diagnostic technologies (7,8), although implementation and scale-up have posed major challenges (9).…”