Diagnostic accuracy of GeneXpert MTB/RIF assay for detection of tubercular pleural effusion.

Jyoti Jain,Preetam Salunkhe,Pooja Jadhao,Shashank Banait,Seyed Ehtesham Hasnain

doi:10.1371/journal.pone.0251618

Jyoti Jain, Preetam Salunkhe + Show 3 more

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https://doi.org/10.1371/journal.pone.0251618

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Abstract

India has been engaged in tuberculosis (TB) control activities for over 50 years and yet TB continues to remain India's important public health problem. The present study was conducted to compare the performance of GeneXpert MTB/RIF (GXpert) assay with composite reference standard in diagnosing cases of tubercular pleural effusion (TPE) and to evaluate the reliability of rifampicin resistance. A cross-sectional study was performed in a Department of Medicine of a rural teaching tertiary care hospital in central India. In all consecutive patients with pleural effusion on chest radiograph presenting to Department of Medicine, GXpert assay and composite reference standard was performed to evaluate the diagnostic accuracy of GXpert assay for detecting TPE in comparison to composite reference standard. Standard formulae were used to calculate the sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), positive likelihood ratios (LR+) and negative likelihood ratios (LR-). Mc-Nemar's test was applied to compare variables. All comparisons were two-tailed. We considered the difference to be statistically significant if the P value was less than 0.05. The sensitivity of the GXpert assay in diagnosing TPE was 16.6% among 158 study participants, the specificity was 100% and diagnostic accuracy was 52.5% which was statistically significant (p value < 0.05). It had a PPV of 100% (95%CI: 88.3% - 100%) and a NPV of 47.5% (95%CI: 39.3% - 55.7%). The LR+ and LR-were 23.5 (95%CI: 1.43-38.6) and 0.83 (95%CI: 0.76-0.91) respectively. GXpert assay has a very high specificity in diagnosing TPE but has a low sensitivity. In comparison to composite reference standard Thus its clinical utility is limited when used as a standalone test. A physician's clinical acumen in combination with routine pleural fluid analysis should be the key factor in the diagnosis of TPE in clinically and radiologically suspected patients, especially in high TB burden countries.

Highlights

Tuberculosis is one of the oldest diseases known to affect humans [1]
In high TB burden settings, diagnosis of Tubercular pleural effusion (TPE) is concluded by exudative pleural fluid with positive adenosine deaminase (ADA) levels along with lymphocytic predominance [4]
Our study revealed pleural fluid Ziehl Neelsen (ZN) microscopy for acid fast bacilli (AFB) as well as growth on Mycobacterial Growth Indicator Tube (MGIT) liquid culture medium was negative in all the study subjects

Summary

Introduction

Tubercular pleural effusion (TPE) is the second commonest form of extra pulmonary tuberculosis after TB lymphadenitis [2]. Major challenges in the diagnosis of extra pulmonary TB are its atypical clinical presentation, difficulties in obtaining specimens and the paucibacillary nature of the disease [3, 4]. Demonstrating the organism in pleural fluid by conventional microbiological techniques (staining and/or culture) have long been the cornerstone in diagnosing TPE [3]. These techniques have low sensitivity and long turnaround time of several weeks which is too long for a diagnostic test to be effective in curbing transmission [5].

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