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Updated: Jun 20, 2025
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Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
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Navigating Diagnostic Pitfalls: False Positivity in GeneXpert Mycobacterium Tuberculosis/Rifampicin Assay
Mahavir Bagrecha1, Siri Vineeth A Ganta1, Shahzad Mirza2
1Respiratory Medicine, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, IND.
Cureus
|July 23, 2024
Summary
The GeneXpert MTB/RIF assay can detect Mycobacterium tuberculosis (MTB) DNA, but may yield false positives in pulmonary tuberculosis (PTB) cases. This highlights challenges in diagnosing active PTB, especially in patients without typical symptoms.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), presents diagnostic challenges, particularly pulmonary TB (PTB) spread via aerosols.
- Traditional sputum culture is slow, costly, and prone to contamination.
- The GeneXpert MTB/RIF (Xpert) assay offers rapid detection of MTB and rifampicin resistance.
Observation:
- This case series examines three patients with pulmonary TB diagnosed via Xpert.
- These patients lacked conventional TB symptoms.
- The Xpert assay detects both live and non-viable MTB DNA.
Findings:
- The Xpert assay can produce false-positive results for pulmonary TB.
- This occurs when detecting DNA from non-viable MTB, such as in patients with prior TB or from contaminated samples.
- The cases demonstrate diagnostic limitations of molecular assays in specific clinical contexts.
Implications:
- Rethinking diagnostic strategies for pulmonary TB is crucial.
- Clinical correlation is essential when interpreting molecular diagnostic results.
- Further research is needed to differentiate between active and residual/non-viable MTB infections.
