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

Abstract

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.

Effect Analysis of the HFMEA Model Applied in Sputum Specimen Management Among Patients with Tuberculosis

“… 7 Diagnostic errors not only result in valuable treatment time loss for patients but also bring financial loss to the laboratory. 8 Consequently, high-quality sputum collection training and patient nursing education play an important role in improving sputum quality, thereby minimising these errors.…”

Evaluating the Sensitivity of Different Molecular Techniques for Detecting Mycobacterium tuberculosis Complex in Patients with Pulmonary Infection

“…The GeneXpert MTB/RIF has been used to detect MTBC DNA ( Horne et al 2019 ). However, such a detection method suffers from low sensitivity when applied directly to pulmonary and/or extra-pulmonary samples ( Mechal et al 2019 ; Rimal et al 2022 ; Sinshaw et al 2022 ). The molecular-based methods for genomic investigation of the MTBC members assisted in introducing other rapid identification methods for diagnosing MDR-TB isolates.…”