Comparative Performance Between Xpert Mtb/Rif Assay, Led Fluorescence Microscopy, and Zn Light Microscopy for Detection of Mycobacterium Tuberculosis In Sputum Samples in Addis Ababa, Ethiopia
Creators: name: Dejene, Daniel
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2014

description: Background: In Ethiopia, the main tool used to diagnosis pulmonary tuberculosis is Ziehl- Neelsen microscopy. The emergence of drug-resistant forms of tuberculosis which needs more resources to detect, to successfully treat and effectively reduce the burden is among the top challenges in the country. Tuberculosis case detection among vulnerable population groups including children, HIV positives and other high risk groups remains low due to insensitive diagnostic tools. Due to its low sensitivity, Ziehl-Neelsen microscopy does not detect all positive TB cases among TB suspects; as a result tuberculosis transmission by false negative cases increases. Therefore, there is a need to assess the incremental value of new diagnostic tool like Xpert MTB/RIF assay and Light Emitted Diode Fluorescent microscopy for tuberculosis detection in our setting. Objective of the study: To determine the performance of Xpert MTB/RIF assay in comparison with Light Emitted Diode Fluorescent microscopy and Ziehl-Neelsen smear microscopy for detection of Mycobacterium Tuberculosis in sputum samples in Addis Ababa. Methods and Materials: A prospective cross-sectional study from December, 2013 to April, 2014 was conducted in AAHRL to compare the performance of light emitting diode fluorescent microscopy (LED-FM), Xpert MTB/RIF assay and Ziehl-Neelsen(ZN) smear microscopy in the diagnosis of pulmonary tuberculosis (PTB) Adult patients. LJ culture media was used as the gold standard for sub-samples. All data was entered into an excel spreadsheet, then transfer and analyzed using SPSS version 20. Descriptive statistics was performed and data presented in tables. McNamara's and Kappa statistics was used for proportion and the percent agreement analysis. Results: A total of 358 pulmonary tuberculosis and MDR-TB (Multi drug resistance tuberculosis) suspected patients were enrolled from December, 2013 to April, 2014 in Addis Ababa Health research and Laboratory with mainly young adults of median age 30.5. After excluding 8 samples that were invalid by Xpert MTB/RIF assay 350 samples were analyzed statistically and The percent agreement between Light Emitted Diode Fluorescent microscopy and Ziehl-Neelsen smear microscopy, Xpert MTB/RIF assay and Light Emitted Diode Fluorescent microscopy, Xpert MTB/RIF assay and Ziehl-Neelsen smear microscopy for MTB detection showed that k=75%(95%CI,67% to 81%), p&lt;.0005, k=81.8%(95%CI, 81% to 82.6%) p&lt;.0005 and k=72.6%(95%CI,61.6%to82.6%), p&lt;.0005, respectively. The percent agreement of the three tests showed that there were an overall percent agreement of 87.4%, 84.6%, and 90.9% between Light Emitted Diode Fluorescent microscopy and Ziehl-Neelsen microscopy, Xpert MTB/RIF assay and Ziehl-Neelsen microscopy, and Light Emitted Diode Fluorescent microscopy and Xpert MTB/RIF assay respectively. In the sub group study the sensitivity, specificity, PPV and NPV achieved with direct Ziehl-Neelsen microscopy, Light Emitted Diode Fluorescent microscopy and Xpert MTB/RIF using culture as a gold standard in 167(47%) samples were (76.9%, 96%, 97.8% and 64%), (81.2%, 90%, 95%, 67.2%) and (89.7%, 92%, 96.3%, 86.2%) respectively. Conclusion: Xpert MTB/RIF assay has better yield than Light Emitted Diode Fluorescent smear microscopy and Ziehl-Neelsen smear microscopy with incremental yield of 12.8% and Light Emitted Diode Fluorescent smear microscopy has better yield than Ziehl-Neelsen smear microscopy with incremental yield of 4.8% therefore Xpert MTB/RIF assay is a highly accurate diagnostic tool for MTB detection, which achieves a substantial reduction in diagnostic delay With overall performance characteristics that are superior to Light Emitted Diode Fluorescent smear microscopy and Ziehl-Neelsen smear microscopy. Keywords: Light Emitting Diode Fluorescent Microscopy (LED-FM), Ziehl-Neelsen (ZN), Xpert MTB/RIF assay