Second-line probe assays (e.g., GenoType MTBDRsl)Ĩ6 (FLQ resistance), 87 (SLID resistance)ĩ9 (FLQ resistance), 99 (SLID resistance) MTB diagnosis and RIF resistance detection For new tests to have impact, they must be adopted and scaled up ( 13). A similar trend of low uptake of new TB tests has also been reported for urine lipoarabinomannan (LAM) testing ( 12). A 2018 study showed that despite a high diagnostic accuracy and quick time to results, the ratio of smear microscopy tests to Xpert tests performed in 17 countries with a high TB burden was 6 to 1 ( 11). However, simply developing new tests is insufficient for ensuring their implementation in countries with the highest TB burdens, and barriers to scale-up molecular tests like Xpert MTB/RIF have been identified ( 10). More than ever before, new assays are emerging and undergoing validation for TB and TB drug-resistance detection. Since the Xpert MTB/RIF assay (Cepheid, Sunnyvale, USA) was first endorsed in 2010, advances in the field of TB diagnostics have mostly been in the realm of NAATs and responsive to the needs articulated by published target product profiles (TPPs) ( 8, 9). 1 and Table 1, there are several molecular TB tests that are already WHO recommended and commercially available. For advances in biomarker-based tests for active and latent TB detection, we refer the readers to other review articles ( 6, 7).Īs shown in Fig. Here, we review recent advances in the field of molecular diagnostics for TB and relevant WHO policies and describe the emerging landscape. As such, they are disrupting the field of TB diagnostics and are helping to improve the quality of TB care ( 4, 5). NAATs can detect TB and perform drug susceptibility testing (DST) for key drugs, such as rifampin (RIF) and isoniazid (INH), more quickly than conventional mycobacterial culture and are also available at different levels of health care systems. Often referred to as nucleic acid amplification tests (NAATs), these assays rely on amplification of a targeted genetic region of the Mycobacterium tuberculosis complex, typically by PCR. Over the last decade, the field of TB diagnostics has seen advances in the form of new molecular tests. In the context of the ongoing COVID-19 pandemic, it is also important to consider integrating testing for TB and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) since symptoms and testing technologies overlap ( 3). New diagnostic tests and optimized test deployment strategies will be critical for achieving this target ( 2). The World Health Organization (WHO) End TB Strategy calls for finding these missing millions in order to meet the sustainable development goal of ending TB by 2030. Despite the severity of the epidemic, approximately 3 million people with TB were deemed “missing” due to underdiagnosis as well as underreporting to national TB programs ( 1). With an estimated 1.5 million attributable deaths and 10 million new cases in 2018, tuberculosis (TB) is the leading infectious disease killer globally ( 1). Here, we review recent advances and developments in molecular tests for detecting TB as well as anti-TB drug resistance. With respect to drug susceptibility testing, NAATs and next-generation sequencing can provide results substantially faster than traditional phenotypic culture. These developments should increase access to molecular TB testing for larger patient populations. Notably, there is an emergence of molecular tests designed, manufactured, and rolled out in countries with high TB burden, of which some are explicitly aimed for near-patient placement. Currently, a wide array of molecular tests for TB detection is being developed and evaluated, and while some tests are intended for reference laboratory use, others are being aimed at the point-of-care and peripheral health care settings. Importantly, some of these WHO-endorsed tests can detect mycobacterial gene mutations associated with anti-TB drug resistance, allowing clinicians to tailor effective TB treatment. 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. 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 testing.
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