Evaluation of molecular diagnostic test for detection of adult pulmonary tuberculosis: A generic protocol.

BACKGROUND OBJECTIVES: Tuberculosis (TB) continues to be the second most-leading cause of death due to a single infectious agent as of 2022 after COVID-19. Many affordable new molecular diagnostic tools are being developed for early and more accurate diagnosis, especially for low-resource settings in low- and middle-income countries. In this context, there is a need to develop a standardized protocol for validation of new diagnostic tools. Here, we describe a generic protocol for multi-centric clinical evaluation of molecular diagnostic tests for adult pulmonary TB. METHODS: This protocol describes a cross-sectional study in TB reference laboratories in India. Adults (>18 yr) visitng the chest clinics or outpatient departments with symptoms of TB need to be enrolled consecutively till the required sample size of 150 culture positives and 470 culture negatives are met. Mycobacterium tuberculosis (Mtb) culture (mycobacteria growth indicator tube liquid culture) to be used under this protocol as the gold standard and Xpert MTB/RIF molecular test will be used as the comparator. The sputum samples will be tested by smear microscopy, Mtb culture, Xpert MTB/RIF and index molecular test as per the proposed algorithm. The specificity sensitivity, and positive/ negative predictive values are to be calculated for the index test with reference to the gold standard. DISCUSSION: TB diagnosis poses many challenges as it differs with type of disease, age group, clinical settings and type of diagnostic tests/kits used. Globally, different protocols are used by several investigators. This protocol provides standard methods for the validation of molecular tests for diagnosis of adult pulmonary TB, which can be adopted by investigators.

Rapid, point-of-care diagnosis of tuberculosis with novel Truenat assay: Cost-effectiveness analysis for India's public sector.

BACKGROUND: Truenat is a novel molecular assay that rapidly detects tuberculosis (TB) and rifampicin-resistance. Due to the portability of its battery-powered testing platform, it may be valuable in peripheral healthcare settings in India. METHODS: Using a microsimulation model, we compared four TB diagnostic strategies for HIV-negative adults with presumptive TB: (1) sputum smear microscopy in designated microscopy centers (DMCs) (SSM); (2) Xpert MTB/RIF in DMCs (Xpert); (3) Truenat in DMCs (Truenat DMC); and (4) Truenat for point-of-care testing in primary healthcare facilities (Truenat POC). We projected life expectancy, costs, incremental cost-effectiveness ratios (ICERs), and 5-year budget impact of deploying Truenat POC in India's public sector. We defined a strategy "cost-effective" if its ICER was

Impact of rapid molecular diagnostic tests on time to treatment initiation and outcomes in patients with multidrug-resistant tuberculosis, Tamil Nadu, India.

BACKGROUND: India is replacing culture and drug sensitivity testing (CDST) with rapid molecular tests for diagnosing MDR-TB. We assessed the impact of rapid tests on time to initiation of treatment and outcomes in patients with MDR-TB compared with CDST. METHODS: A retrospective cohort study involving MDR-TB patients from six districts in Tamil Nadu state, who underwent CDST (2010-2011) and rapid tests (2012-2013). RESULTS: There were 135 patients in the CDST group and 389 in the rapid diagnostic test group. Median time from sputum receipt at the laboratory to initiation of MDR-TB treatment was 130 days (IQR 75-213) in the CDST group and 22 days (IQR 14-38) in the rapid diagnostic test group (p<0.001). Overall treatment success was 30% with CDST and 41% with rapid tests (p<0.05), but there was high loss to follow-up >30% in both groups and missing data were higher in CDST (13%) compared with rapid tests (3%). There were significantly higher risks of unfavourable treatment outcomes in males (aRR 1.3, 95% CI 1.1-1.5) and those with treatment initiation delays >30 days (aRR 1.3, 95% CI 1.0-1.6). CONCLUSION: Rapid molecular diagnostic tests shortened the time to initiate treatment which was associated with reduced unfavourable outcomes in MDR-TB patients. This supports the policy to scale up these tests in India.

Sputum culture conversion with moxifloxacin-containing regimens in the treatment of patients with newly diagnosed sputum-positive pulmonary tuberculosis in South India.

BACKGROUND: Rapid sputum culture conversion at 2 months indicates the sterilizing capacity and potential of regimens to shorten duration of tuberculosis treatment. We compared results of sputum culture conversion by moxifloxacin and control regimens and identified factors affecting sputum culture positivity after 2 months of treatment. METHODS: Human immunodeficiency virus-uninfected adults with newly diagnosed smear-positive pulmonary tuberculosis were randomized to receive a 3- or 4-month moxifloxacin regimen (moxifloxacin [M], isoniazid [H], rifampicin [R], pyrazinamide [Z], ethambutol [E]) or the control regimen (RHZE thrice weekly). Bacteriological assessments were done at 15, 30, 45, and 60 days of treatment. Because all patients in the moxifloxacin groups received 2 months of daily RHZEM, they were grouped together for analysis. Statistical methods included χ(2) test and logistic regression analysis. RESULTS: Sputum culture conversion was analyzed in 780 (616 in the moxifloxacin group and 164 in the control group) of 801 enrolled patients. Ninety-five percent of 590 patients in the moxifloxacin group and 81% of 151 patients in the control group had negative sputum cultures at month 2 (P < .001). The control regimen, age (≥35 years), initial sputum culture grade (2+ or 3+), and male sex were significantly associated with higher odds of positive sputum cultures at 2 months. CONCLUSIONS: A 5-drug daily regimen with moxifloxacin results in significantly higher sputum culture conversion in the first 2 months compared with a thrice-weekly, 4-drug regimen in patients with newly diagnosed sputum-positive pulmonary tuberculosis.