Validation of the FluoroType® MTBDR assay using respiratory and lymph node samples

New insight in molecular detection of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis, is a pathogenic bacterium that has claimed millions of lives since the Middle Ages. According to the World Health Organization's report, tuberculosis ranks among the ten deadliest diseases worldwide. The presence of an extensive array of genes and diverse proteins within the cellular structure of this bacterium has provided us with a potent tool for diagnosis. While the culture method remains the gold standard for tuberculosis diagnosis, it is possible that molecular diagnostic methods, emphasis on the identification of mutation genes (e.g., rpoB and gyrA) and single nucleotide polymorphisms, could offer a safe and reliable alternative. Over the past few decades, as our understanding of molecular genetics has expanded, methods have been developed based on gene expansion and detection. These methods typically commence with DNA amplification through nucleic acid targeted techniques such as polymerase chain reaction. Various molecular compounds and diverse approaches have been employed in molecular assays. In this review, we endeavor to provide an overview of molecular assays for the diagnosis of tuberculosis with their properties (utilization, challenges, and functions). The ultimate goal is to explore the potential of replacing traditional bacterial methods with these advanced molecular diagnostic techniques.

Diagnostic value of nucleic acid amplification tests for tuberculous pleural effusion

Diagnosing tuberculous pleural effusion (TPE) is challenging for pulmonologists and laboratory scientists. The gold standards for TPE diagnosis are pleural fluid Ziehl-Neelsen staining, Mycobacterium tuberculosis (Mtb) culture and pleural biopsy. These tools have limitations, including low sensitivity, long turnaround time and invasiveness. The nucleic acid amplification test (NAAT) is a rapid and minimally invasive tool for diagnosing TPE. This review summarizes the diagnostic accuracy of available NAATs for TPE, with a focus on the evidence from systematic reviews and meta-analyses. The NAATs summarized in this review include in-house NAATs, GeneXpert-MTB/RIF, GeneXpert-MTB/RIF Ultra, simultaneous amplification and testing-tuberculosis, FluoroType MTB and loop-mediated isothermal amplification.

FluoroType® MTB in pleural fluid for diagnosing tuberculosis

OBJECTIVES

This work aims to investigate the diagnostic accuracy of a nucleic acid amplification test (FluoroType MTB®) in pleural fluid (PF) and sputum to diagnose tuberculous pleural effusion (TPE). We also analyzed the increase in diagnostic accuracy of a second FluoroType MTB® test on a second thoracentesis sample when the first was negative.

METHODS

We conducted a prospective single-center study that included 207 patients with pleural effusion (31 tuberculous and 176 due to other causes). Of the 31 cases of TPE, 21 (68%) were confirmed histologically or microbiologically; the other cases were considered probable.

RESULTS

The operational characteristics of FluoroType MTB® in PF for identifying tuberculosis were a sensitivity of 13%, a specificity of 99%, a positive likelihood ratio of 11, and a negative likelihood ratio of 0.9. The diagnostic efficacy data for sputum samples were 21%, 91%, 2.4, and 0.9, respectively. PF and sputum cultures in solid and liquid media had greater sensitivity (36% and 31%, respectively). A second FluoroType MTB® test in PF was negative for 24 patients who had TPE and for whom the first FluoroType MTB® test was also negative. Only two (6.5%) patients with TPE had a confirmed diagnosis based exclusively on the positive results of the FluoroType MTB® in PF.

CONCLUSION

Due to its low sensitivity, the FluoroType MTB® test in PF has a limited role in diagnosing tuberculous pleurisy.

Diagnostic accuracy of centralised assays for TB detection and detection of resistance to rifampicin and isoniazid: a systematic review and meta-analysis

Various diagnostic companies have developed high throughput molecular assays for tuberculosis (TB) and resistance detection for rifampicin and isoniazid. We performed a systematic review and meta-analyses to assess the diagnostic accuracy of five of these tests for pulmonary specimens. The tests included were Abbott RealTime MTB, Abbott RealTime RIF/INH, FluoroType MTB, FluoroType MTDBR and BD Max MDR-TB assay.A comprehensive search of six databases for relevant citations was performed. Cross-sectional, case-control, cohort studies, and randomised controlled trials of any of the index tests were included. Respiratory specimens (such as sputum, bronchoalveolar lavage, tracheal aspirate, etc) or their culture isolates.A total of 21 included studies contributed 26 datasets. We could only meta-analyse data for three of the five assays identified, as data were limited for the remaining two. For TB detection, the included assays had a sensitivity of 91% or more and the specificity ranged from 97% to 100%. For rifampicin resistance detection, all the included assays had a sensitivity of more than 92%, with a specificity of 99-100%. Sensitivity for isoniazid resistance detection varied from 70 to 91%, with higher specificity of 99-100% across all index tests. Studies that included head-to-head comparisons of these assays with Xpert MTB/RIF for detection of TB and rifampicin resistance suggested comparable diagnostic accuracy.In people with symptoms of pulmonary TB, the centralised molecular assays demonstrate comparable diagnostic accuracy for detection of TB, rifampicin and isoniazid resistance to Xpert MTB/RIF assay, a WHO recommended molecular test.

FluoroType® MTB in pleural fluid for diagnosing tuberculosis

OBJECTIVES

This work aims to investigate the diagnostic accuracy of a nucleic acid amplification test (FluoroType MTB®) in pleural fluid (PF) and sputum to diagnose tuberculous pleural effusion (TPE). We also analyzed the increase in diagnostic accuracy of a second FluoroType MTB® test on a second thoracentesis sample when the first was negative.

METHODS

We conducted a prospective single-center study that included 207 patients with pleural effusion (31 tuberculous and 176 due to other causes). Of the 31 cases of TPE, 21 (68%) were confirmed histologically or microbiologically; the other cases were considered probable.

RESULTS

The operational characteristics of FluoroType MTB® in PF for identifying tuberculosis were a sensitivity of 13%, a specificity of 99%, a positive likelihood ratio of 11, and a negative likelihood ratio of 0.9. The diagnostic efficacy data for sputum samples were 21%, 91%, 2.4, and 0.9, respectively. PF and sputum cultures in solid and liquid media had greater sensitivity (36% and 31%, respectively). A second FluoroType MTB® test in PF was negative for 24 patients who had TPE and for whom the first FluoroType MTB® test was also negative. Only two (6.5%) patients with TPE had a confirmed diagnosis based exclusively on the positive results of the FluoroType MTB® in PF.

CONCLUSION

Due to its low sensitivity, the FluoroType MTB® test in PF has a limited role in diagnosing tuberculous pleurisy.