Diagnostic value of polymerase chain reaction/acid-fast bacilli in conjunction with computed tomography-guided pleural biopsy in tuberculous pleurisy: A diagnostic accuracy study

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.

Diagnosis of pleural tuberculosis by multi-targeted loop-mediated isothermal amplification assay based on SYBR Green I reaction: comparison with GeneXpert® MTB/RIF assay

BACKGROUND

Diagnosis of pleural tuberculosis (TB) is tedious owing to its close resemblance with malignant pleural effusion and sparse bacterial load in clinical specimens. There is an immediate need to design a rapid and dependable diagnostic test to prevent unnecessary morbidity/mortality.

RESEARCH DESIGN AND METHODS

A multi-targeted loop-mediated isothermal amplification (MT-LAMP) was deliberated using mpt64 and IS6110 to diagnose pleural TB within pleural fluids/biopsies. MT-LAMP products were analyzed by gel-based and visual detection methods, viz. SYBR Green I, SYBR Green I+deoxyuridine triphosphate uracil-N-glycosylase (dUTP-UNG), and dry methyl green reactions.

RESULTS

In a pilot study, while assessing pleural TB/non-TB control subjects (n = 40), both SYBR Green I+dUTP-UNG/gel-based MT-LAMP assays exhibited better sensitivity/specificity than SYBR Green I and dry methyl green MT-LAMP. Since it is facile to work with SYBR Green I+dUTP-UNG than gel-based MT-LAMP, we validated the performance of SYBR Green I+dUTP-UNG in a higher number of specimens (n = 97), which revealed somewhat higher sensitivity (85.2 vs. 81.5%) and specificity (97.7 vs. 90.7%) than SYBR Green I MT-LAMP. Furthermore, the sensitivity attained by SYBR Green I+dUTP-UNG MT-LAMP was significantly higher (p < 0.001) than GeneXpert.

CONCLUSIONS

Our SYBR Green I+dUTP-UNG MT-LAMP is a simple and reliable method to diagnose pleural TB, which may translate into a point-of-care test.

Use of Pleural Fluid Digital PCR Analysis to Improve the Diagnosis of Pleural Tuberculosis

The diagnosis of pleural tuberculosis (TB) remains difficult due to the paucity of Mycobacterium tuberculosis in pleural fluid (PF). This study aimed to improve pleural TB diagnosis using highly sensitive digital PCR (dPCR) technique. A total of 310 patients with evidence of PF were consecutively enrolled, 183 of whom suffered from pleural TB and 127 from non-TB. PF samples were prospectively collected and total DNA was extracted. The copy numbers of M. tuberculosis insertion sequence (IS) 6110 and IS1081 in DNA were quantified using dPCR. The overall area under the curve of IS6110-dPCR was greater than that of IS1081-dPCR (0.85 versus 0.79). PF IS6110 OR IS1081-dPCR (according to their cut-off values, "positive" was defined as either of them was positive, while "negative" was defined as both of them were negative) had higher sensitivity and equal specificity compared with single target-dPCR. The sensitivity of PF IS6110 OR IS1081-dPCR for total, definite, and probable pleural TB was 59.0% (95% CI = 51.5% to 66.2%), 72.8% (95% CI = 62.6% to 81.6%), and 45.1% (95% CI = 34.6% to 55.8%), respectively. Its specificity was 100% (95% CI = 97.1% to 100.0%). PF IS6110 OR IS1081-dPCR showed a higher sensitivity than smear microscopy (57.4% versus 7.1%), mycobacterial culture (55.3% versus 31.8%), and Xpert MTB/RIF (57.6% versus 23.0%). Long antituberculosis treatment time (>1 month) was found to be associated with negative dPCR results in pleural TB patients. This study indicates that PF IS6110 OR IS1081-dPCR is an accurate molecular assay, which is more sensitive than routine etiological tests and has the potential to enhance the definite diagnosis of pleural TB. IMPORTANCE Pleural TB is one of the most frequent causes of pleural effusion, especially in areas with high burden of TB. Due to the paucibacillary nature of the disease, the diagnostic sensitivities of all available bacteriological and molecular tests remain poor. There is an urgent need to develop new efficient methods. Digital PCR (dPCR) is the third generation of PCR that enables the exact quantification of trace nucleic acids in samples. This study evaluates the diagnostic performance of pleural fluid (PF) dPCR analysis for pleural TB, and shows that PF IS6110 OR IS1081-dPCR has a higher sensitivity than routine etiological tests such as smear microscopy, mycobacterial culture, and Xpert MTB/RIF. This work provides a new choice for improving the definite diagnosis of pleural TB.

Insight into diagnosis of pleural tuberculosis with special focus on nucleic acid amplification tests

INTRODUCTION

Pleural tuberculosis (TB) is the archetype of extrapulmonary TB (EPTB), which mainly affects the pleural space and leads to exudative pleural effusion. Diagnosis of pleural TB is a difficult task predominantly due to atypical clinical presentations and sparse bacillary load in clinical specimens.

AREA COVERED

We reviewed the current literature on the globally existing conventional/latest modalities for diagnosing pleural TB. Bacteriological examination (smear/culture), tuberculin skin testing/interferon-γ release assays, biochemical testing, imaging and histopathological/cytological examination are the main modalities. Moreover, nucleic acid amplification tests (NAATs), i.e. loop-mediated isothermal amplification, PCR/multiplex-PCR, nested-PCR, real-time PCR and GeneXpert® MTB/RIF are being utilized. Currently, GeneXpert Ultra, Truenat MTB^TM, detection of circulating Mycobacterium tuberculosis (Mtb) cell-free DNA by NAATs, aptamer-linked immobilized sorbent assay and immuno-PCR (I-PCR) have also been exploited.

EXPERT OPINION

Routine tests are not adequate for effective pleural TB diagnosis. The latest molecular/immunological tests as discussed above, and the other tools, i.e. real-time I-PCR/nanoparticle-based I-PCR and identification of Mtb biomarkers within urinary/serum extracellular vesicles being utilized for pulmonary TB and other EPTB types may also be exploited to diagnose pleural TB. Reliable diagnosis and early therapy would reduce the serious complications associated with pleural TB, i.e. TB empyema, pleural fibrosis, etc.

Diagnostic value of Xpert MTB/RIF assay on pleural tissue obtained via closed pleural biopsy among persons with presumptive tuberculous pleuritis

Background

Tuberculous pleuritis (TBP) is a common extrapulmonary tuberculosis that contributes to the tuberculosis burden. Xpert MTB/RIF assay is a promising method for rapid diagnosis of TBP. The diagnostic value of Xpert MTB/RIF assay in pleural tissue obtained via closed pleural biopsy among sputum acid-fast bacilli (AFB) smear-negative persons is not well studied.

Objectives

To evaluate the diagnostic value of Xpert MTB/RIF assay on diagnosis of TB in pleural tissue obtained via blind closed pleural biopsy.

Methods

Closed pleural biopsy using Cope needle was performed on adult patients who presented with lymphocyte predominant exudative pleural effusion. Xpert MTB/RIF assay was performed in parallel to pathology and mycobacterial culture of the pleural tissue specimen to determine its sensitivity and specificity. Final clinical diagnosis of TBP was determined by improvement in 2-months follow-up of anti-tuberculous treatment.

Results

A total of 33 patients were included in the study. The median (interquartile range (IQR)) age was 27 (25 - 42) years. The sensitivity and specificity of Xpert MTB/RIF assay was 30% and 100% compared with Mycobacterium tuberculosis culture as the gold standard, and 20% and 95.7% compared with histopathology as the gold standard.

Conclusion

Xpert MTB/RIF assay in pleural tissue obtained by closed pleural biopsy did not increase diagnostic yield, but it shortens time for diagnosis compared with conventional methods.

Application of acid-fast staining combined with GeneXpert MTB/RIF in the diagnosis of non-tuberculous mycobacteria pulmonary disease

OBJECTIVE

To evaluate the clinical diagnostic value of positive acid-fast staining combined with negative GeneXpert MTB/RIF in the diagnosis of non-tuberculous mycobacteria pulmonary disease (NTM-PD).

METHODS

A total of 133 inpatients with confirmed NTM-PD were included consecutively between January 1, 2018 and December 31, 2019, at Tongji Hospital and Jinyintan Hospital, Tongji Medical College of Huazhong University of Science and Technology, in Wuhan, China. One hundred patients with confirmed pulmonary tuberculosis (PTB) were randomly included as the control group.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of positive acid-fast staining combined with a negative GeneXpert MTB/RIF result were 51.13% (95% confidence interval (CI) 42.52-59.73%), 97.00% (95% CI 93.60-100.40%), 95.78% (95% CI 90.98-100.57%), and 59.88% (95% CI 52.25-67.51%), respectively. When subjects were limited to patients with positive acid-fast staining, the sensitivity of a negative GeneXpert MTB/RIF result was 88.31% (95% CI 80.97-95.65%). When acid-fast staining was conducted ≥3 times, the sensitivity of this combination diagnosis method increased to 61.67% (95% CI 49.00-74.33%).

CONCLUSIONS

Positive acid-fast staining combined with a negative GeneXpert MTB/RIF result could be an effective and time-saving method for the diagnosis of NTM-PD.