Molecular detection of Mycobacterium tuberculosis in blood stained sputum samples using GeneXpert PCR assay

Quality Assurance for Hepatitis C Virus Point-of-Care Diagnostics in Sub-Saharan Africa

As part of a multinational study to evaluate the Bioline Hepatitis C virus (HCV) point-of-care (POC) testing in sub-Saharan Africa (SSA), this narrative review summarises regulatory standards and quality indicators for validating and approving HCV clinical diagnostics. In addition, this review also provides a summary of their diagnostic evaluations using the REASSURED criteria as the benchmark and its implications on the WHO HCV elimination goals 2030.

Diagnosis of Chest Wall Tuberculosis Using Fine Needle Aspiration: A Single-Center Experience

Introduction

Minimally invasive diagnosis of chest wall tuberculosis remains a challenge. Fine needle aspiration (FNA) is a simple and safe method of sampling. However, previous studies have shown that conventional tuberculosis tests had poor diagnostic performance in the needle aspirates. With the popularization of molecular detection application, the value of FNA in the diagnosis of chest wall tuberculosis needs to be reevaluated.

Methods

We retrospectively studied patients with suspected chest wall tuberculosis at admission who underwent FNA for diagnosis and reported the diagnostic efficacy of acid-fast bacilli smear, mycobacterial culture, cytology and Xpert MTB/RIF (GeneXpert) when testing FNA specimens. A composite reference standard (CRS) was used as the diagnostic gold standard for this study.

Results

Among 89 included FNA specimens, acid-fast bacilli smear, mycobacterial culture, and GeneXpert were positive in 15 (16.85%), 23 (25.8%), and 61 (68.5%), respectively. Thirty-nine (43.8%) had cytologic features suggestive of tuberculosis. According to CRS, 75 (84.3%) cases were categorized as chest wall tuberculosis, 14 (15.7%) were not diagnosed with tuberculosis. Using CRS as the gold standard, acid-fast bacilli smear, mycobacterial culture, cytology and GeneXpert exhibited sensitivity of 20%, 30.7%, 52% and 81.3%, respectively. Specificity in these four tests was found to be 100%. Sensitivity of GeneXpert was significantly higher than that of smear, culture and cytology, X ₂=66.3, p<0.001.

Conclusion

GeneXpert achieved higher sensitivity as compared to cytology and conventional TB tests in the chest wall FNA specimens. The implementation of GeneXpert may increase the diagnostic efficacy of FNA in the diagnosis of chest wall TB.

The Value of GeneXpert MTB/RIF for Detection in Tuberculosis: A Bibliometrics-Based Analysis and Review

With the continuous development of medical science and technology, especially with the advent of the era of precision diagnosis and treatment, molecular biology detection technology is widely valued and applied as an aid to early diagnosis of tuberculosis. The GeneXpert Mycobacterium tuberculosis Branching (MTB) technology is a suite of semi-nested real-time fluorescent quantitative PCR in vitro diagnostic technologies developed by Cepheid Inc. It targets the rifampicin resistance gene, rpoB, and can detect both MTB and resistance to rifampicin within 2 h. This review analyzed the papers related to GeneXpert using bibliometric software CiteSpace and Bibliometrix. A total of 151 articles were analyzed, spanning from 2011 to 2021. This bibliometrics-based review summarizes the history of the development of GeneXpert in tuberculosis diagnosis and its current status. Contributions of different countries to the topic, journal analysis, key paper analysis, and clustering of keywords were used to analyze this topic.

Effect of sputum quality and role of Xpert® MTB/ RIF assay for detection of smear-negative pulmonary tuberculosis in same-day diagnosis strategy in Addis Ababa, Ethiopia

Background

There is limited information on the performance of the Xpert® MTB/RIF test for diagnosis of smear-negative pulmonary tuberculosis (SNPT) and rifampicin resistance (RR) in the same-day diagnosis approach. The effects of sputum quality and other factors affecting the Xpert performance are also under-investigated.

Objective

This study aimed to determine the performance of the Xpert® MTB/RIF test for detection of SNPT and RR in the same-day diagnosis strategy and the effect of sputum quality and other factors on its performance.

Methods

A cross-sectional study was conducted from August 2017 to January 2018 across 16 health facilities in Addis Ababa, Ethiopia. Two spot sputum samples were collected from 418 presumptive SNPT patients, tested with Xpert® MTB/RIF, then compared to tuberculosis culture. Additionally, culture isolates were tested for RR by BACTEC MGIT™ 960 drug susceptibility testing (DST) and MTBDRplus version 2.

Results

The Xpert® MTB/RIF test detected 24 (5.7%) SNPT cases, with a sensitivity of 92.3% (75.9% - 97.9%) and specificity of 99.2% (97.8% - 99.7%) compared with tuberculosis culture. Xpert® MTB/RIF also detected three (11.58%) RR strains with 100.0% concordance with BACTEC MGIT™ 960 DST and MTBDRplus results. Three blood-stained SNPT samples were positive by Xpert (30.0%), which was 6.9 times higher compared to salivary sputum (odds ratio: 6.9, 95% confidence interval: 1.36-34.96, p = 0.020).

Conclusion

The performance of the Xpert® MTB/RIF to detect SNPT and RR in same-day diagnosis is high. However, SNPT positivity varies among sputum qualities, and good sample collection is necessary for better test performance.