Low diagnostic accuracy of Xpert MTB/RIF assay for extrapulmonary tuberculosis: A multicenter surveillance

Mohammadreza Allahyartorkaman,Gholamreza Hamzehloo,Mohammad Javad Nasiri,Mehdi Mirsaeidi,Mona Zakiloo,Sirus Amini

doi:10.1038/s41598-019-55112-y

Mohammadreza Allahyartorkaman, Gholamreza Hamzehloo + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-55112-y

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Abstract

Diagnostic accuracy of Xpert MTB/RIF assay for pulmonary tuberculosis (PTB) and extrapulmonary TB (EPTB) has not been investigated in Iran. This study was aimed to assess the diagnostic accuracy of Xpert MTB/RIF assay for both PTB and EPTB. A total of 2111 clinical samples (1218 pulmonary and 838 extra-pulmonary) were collected from 16 medical centers during the study period and were analyzed for detection of PTB and EPTB by both Xpert MTB/RIF assay and standard conventional methods (culture and direct smear microscopy). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Xpert MTB/RIF assay for PTB were found to be 95.5%, 96.7%, 83.8%, and 99.1% respectively. For EPTB, the sensitivity, specificity, PPV and NPV of Xpert MTB/RIF assay counted for 76.5%, 95.9%, 62%, and 97.9% respectively. Xpert MTB/RIF assay found to be highly sensitive, specific and comparable to standard conventional methods for the diagnosis of PTB. However, the sensitivity and specificity of Xpert MTB/RIF for EPTB specimens were highly variable; thus, Xpert MTB/RIF cannot be recommended to replace standard conventional tests for diagnosis of EPTB.

Highlights

Tuberculosis (TB) still remains a public health problem with an increasing death rate worldwide, especially in developing countries[1]
The current study was aimed to comprehensively analyze the diagnostic accuracy of Xpert MTB/RIF assay for pulmonary tuberculosis (PTB) and extrapulmonary TB (EPTB) in Iran
The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Xpert MTB/ RIF assay for PTB were found to be 95.5%, 96.7%, 83.8%, and 99.1% respectively

Summary

Introduction

Tuberculosis (TB) still remains a public health problem with an increasing death rate worldwide, especially in developing countries[1]. In the context of these limitations, Xpert MTB/RIF assay, a fully automated real-time semi-nested PCR system was endorsed by World Health Organization (WHO) as the most rapid test for diagnosis of pulmonary TB (PTB)[7]. From PTB, the diagnosis of EPTB is still a serious problem and existing tests are limited in accuracy[8]. Xpert MTB/RIF assay has been validated for TB detection in sputum by authors in different countries, the efficacy of this automated molecular platform for TB detection in nonrespiratory specimens was highly variable, as its sensitivity ranged from 30% to 100%16–26. The current study was aimed to comprehensively analyze the diagnostic accuracy of Xpert MTB/RIF assay for PTB and EPTB in Iran

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