Original Research

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

Waganeh Sinshaw, Abebaw Kebede, Adane Bitew, Mengistu Tadesse, Zemedu Mehamed, Ayinalem Alemu, Bazezew Yenew, Misikir Amare, Biniyam Dagne, Getu Diriba, Ephrem Tesfaye, Dinka F. Gamtesa, Yeshiwork Abebaw, Helina Mollalign, Getachew Seid, Muluwork Getahun
African Journal of Laboratory Medicine | Vol 11, No 1 | a1671 | DOI: https://doi.org/10.4102/ajlm.v11i1.1671 | © 2022 Waganeh Sinshaw, Abebaw Kebede, Adane Bitew, Mengistu Tadesse, Zemedu Mehamed, Ayinalem Alemu, Bazezew Yenew, Misikir Amare, Biniyam Dagne, Getu Diriba, Ephrem Tesfaye, Dinka F. Gamtesa, Yeshiwork Abebaw, Helina Molallign Mollalign, Getachew Seid, Muluwor | This work is licensed under CC Attribution 4.0
Submitted: 08 July 2021 | Published: 31 August 2022

About the author(s)

Waganeh Sinshaw, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia; and, Department of Microbiology, Immunology and Parasitology, School of Medicine, Addis Ababa University, Addis Ababa, Ethiopia; and, Department of Medical Laboratory Science, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
Abebaw Kebede, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia; and, Department of Microbial, Cellular, and Molecular Biology, College of Natural and Computational Sciences, Addis Ababa University, Addis Ababa, Ethiopia
Adane Bitew, Department of Medical Laboratory Science, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
Mengistu Tadesse, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Zemedu Mehamed, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Ayinalem Alemu, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Bazezew Yenew, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Misikir Amare, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Biniyam Dagne, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Getu Diriba, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Ephrem Tesfaye, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Dinka F. Gamtesa, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Yeshiwork Abebaw, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Helina Mollalign, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Getachew Seid, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
Muluwork Getahun, Tuberculosis Research Unit/National Tuberculosis Reference Laboratory, Ethiopian Public Health Institute, 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.


Keywords

smear-negative pulmonary tuberculosis; Xpert® MTB/RIF test; sputum quality; tuberculosis culture; diagnostic performance

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