Multigene Mycobacterium tuberculosis cell-free DNA assay.

Area of Science:

• Medical Diagnostics
• Molecular Biology
• Infectious Diseases

Background:

• Current tuberculosis diagnostics often rely on sputum, posing collection challenges.
• Plasma Mycobacterium tuberculosis cell-free DNA (Mtb cfDNA) offers an alternative diagnostic target.

Purpose of the Study:

• To evaluate a quantitative PCR (qPCR) assay using plasma Mtb cfDNA for pulmonary TB diagnosis.
• To assess the sensitivity and specificity of targeting multiple genes (IS6110, cyp141, devR).

Main Methods:

• Plasma samples from 106 pulmonary TB patients and 60 controls were analyzed.
• A qPCR assay targeted IS6110, cyp141, and devR genes.
• Sensitivity was compared against Xpert MTB/RIF, culture, and clinical diagnosis; specificity against controls.

Main Results:

• The Mtb cfDNA assay achieved 71.7% sensitivity for all PTB cases, higher in bacteriologically confirmed (78.3%) than clinically diagnosed (28.6%) cases.
• Combined specificity was 91.7%.
• Targeting multiple genes, particularly IS6110 and cyp141 (70.8% sensitivity), improved overall detection rates compared to single-gene targets.

Conclusions:

• Plasma Mtb cfDNA quantitative PCR is a potential adjunctive tool for TB diagnosis.
• Multiplex gene targeting enhances the sensitivity of cfDNA-based TB diagnostics.
• This approach may overcome limitations associated with sputum sample collection.