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Published on: June 6, 2025
Accuracy of the Phenotypic 1G Test to Detect Mycobacterium tuberculosis and Drug Resistance From Sputa in the
Mia Aguirre1, Doris Ayala1, Juan Ignacio Garcia2,3
1Department of Epidemiology, School of Public Health, University of Texas Health Science Center at Houston, Brownsville.
Background:
With >10 million new tuberculosis (TB) cases per year, a limitation to TB control is the lack of simple and accurate tests for diagnosis and drug susceptibility testing (DST) in endemic regions. We evaluated the accuracy of the first-generation, low-complexity phenotypic TB test (1G test), designed for simultaneous Mycobacterium tuberculosis (Mtb) detection and resistance to isoniazid, rifampicin, and moxifloxacin, suitable for resource-limited settings.
Methods:
A cross-sectional study was conducted with sputa from 426 possible pulmonary TB cases from 2 small Mexican cities bordering Texas. The 1G test was compared against phenotypic TB detection tests in the region, specifically acid-fast bacilli smear microscopy and Mycobacteria Growth Indicator Tube (MGIT) culture, as well as MGIT-DST for resistance to isoniazid, rifampicin, and moxifloxacin.
Results:
The 1G test demonstrated ≥98% sensitivity for Mtb detection; 100% sensitivity and 91% (rifampicin), 94% (isoniazid), and 97% (moxifloxacin) specificity for DST; and less contamination than the MGIT (3.5% vs 8.1%, P < .05). The 1G test time to detection of Mtb and simultaneous DST was 17 days, while the MGIT-DST required 2 steps: 7 days for Mtb detection plus 14 more days for DST (21 days total). Our study site drug-resistant TB prevalence was 14% when testing all consecutively enrolled participants vs 6% by passive reporting.
Conclusions:
The 1G test is a low-complexity phenotypic TB diagnostic method that is a practical replacement to current culture-based tests. Future studies are warranted to evaluate implementation of the 1G test in decentralized clinics that lack molecular tools, resources, and expertise.
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