A Prospective Comparative Study of Diagnostic Accuracy between TrueNat and GeneXpert for the Diagnosis of Pulmonary Tuberculosis |Chapter 6 | Medical Science: Updates and Prospects Vol. 3

 

Background: Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (MTB), primarily transmitted via airborne particles. The currently recommended methods for diagnosing tuberculosis (TB) include molecular-based tests that can detect both TB and drug-resistant forms of the disease. Enhancing access to reliable and accurate diagnosis of tuberculosis (TB) is a priority for global TB control. Molbio Diagnostics has developed the TrueNat point-of-care molecular assays for detecting TB and rifampicin (RIF) resistance. Until 2020, the Xpert system was the only WHO-recommended option for rapid molecular detection of both TB and rifampin-resistant TB. This study aimed to compare the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of GeneXpert with TrueNat, using the MGIT test as the gold standard.

 

Methods: A cross-sectional comparative study involved 350 patients with suspected pulmonary TB at the Intermediate Reference Laboratory in the Government Hospital for Chest Diseases, Puducherry, India. Sputum samples were collected in pre-sterilised tubes, transported at 2–8°C to the reference laboratory, and processed using the NALC-NaOH method, with aliquots allocated for microscopy, culture, TrueNat, and Xpert testing, while excess was stored at –80°C. The BACTEC-MGIT-960 test is used to detect the growth of M. tuberculosis in drug-containing and drug-free tubes. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy for tuberculosis diagnosis were calculated for TrueNat and GeneXpert and compared to the MGIT results. Data analysis was performed using MedCalc Software Ltd., specifically the Odds Ratio Calculator (Version 23.1.6).

 

Results: Among the 350 patients, 296 (84.57%) tested positive for TB with GeneXpert, while 280 (80.00%) tested positive with TrueNat. For the GeneXpert assay in detecting pulmonary TB in sputum samples, the sensitivity was 98.66%, the specificity was 96.15%, the PPV was 99.32%, the NPV was 92.59%, and the accuracy was 98.29%. In comparison, the TrueNat technique had a sensitivity of 93.22%, specificity of 90.91%, PPV of 98.21%, NPV of 71.43%, and accuracy of 92.86%. The agreement between the TrueNat assay and the GeneXpert method, using the BACTEC-MGIT-960 method for detecting Mycobacterium tuberculosis in pulmonary samples, was significant, with Kappa values of 0.76 (S.E.: 0.05) for TrueNat and 0.93 (S.E.: 0.03) for GeneXpert.

 

Conclusion: Overall, the GeneXpert assay demonstrated greater sensitivity than TrueNat in respiratory samples. It is advisable to interpret TrueNat negative results cautiously and to correlate them closely with the patient's clinical and treatment history.

 

 

Author(s) Details

Balasundaram Revathi Mani
Department of Biochemistry, Queen Mary’s College, Madras, Tamil Nadu, India.

 

Usharani Brammacharry
Institute of Basic Medical Sciences, University of Madras, Chennai, Tamil Nadu, India.

 

Venkateswari Ramachandra
Institute of Basic Medical Sciences, University of Madras, Chennai, Tamil Nadu, India.

 

Muthuraj Muthaiah
Department of Microbiology, State TB Training and Demonstration Centre, Intermediate Reference Laboratory, Government Hospital for Chest Diseases, Puducherry, India.

 

Please see the book here :- https://doi.org/10.9734/bpi/msup/v3/6786