Fluorescence microscopy for the diagnosis of smear-negative pulmonary tuberculosis in Ethiopia
Background: Despite its low sensitivity, microscopy remains the main method for the diagnosis of pulmonary tuberculosis in most laboratories in Ethiopia. Few studies have evaluated the performance of light-emitting diode fluorescent microscopy (LED-FM) in bleach-concentrated smear-negative sputum sp...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
AOSIS
2020-09-01
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Series: | African Journal of Laboratory Medicine |
Subjects: | |
Online Access: | https://ajlmonline.org/index.php/ajlm/article/view/810 |
Summary: | Background: Despite its low sensitivity, microscopy remains the main method for the diagnosis of pulmonary tuberculosis in most laboratories in Ethiopia. Few studies have evaluated the performance of light-emitting diode fluorescent microscopy (LED-FM) in bleach-concentrated smear-negative sputum specimens.
Objective: This study aimed to evaluate the diagnostic performance of LED-FM for smear-negative pulmonary tuberculosis in Ethiopia.
Methods: A total of 194 adult patients with a cough lasting for more than two weeks, and who had three direct smear-negative sputum tests for Mycobacterium tuberculosis by Ziehl-Neelsen light microscopy, were included. All direct Ziehl-Neelsen-stained smear-negative sputum samples were cultured and were also visualised by LED-FM. Smears for LED-FM were performed from bleach-concentrated sputum sediment. The diagnostic performance of the LED-FM was compared to the culture method (the reference standard).
Results: Of the 194 smear-negative sputum specimens analysed, 28 (14.4%) were culture-positive and 21 (10.8%) were LED-FM-positive for M. tuberculosis. However, only 11 of the 21 (52.4%) LED-FM-positive patients had a confirmed tuberculosis diagnosis by culture. Light-emitting diode fluorescence microscopy (FM) had a sensitivity of 39.3% (95% confidence interval: 21.2–57.4) and specificity of 93.9% (95% confidence interval: 90.4–97.6). Ten LED-FM-positive specimens were culture-negative, and all of these specimens had scanty grading (1–19 bacilli per 40 fields on LED-FM).
Conclusion: This study showed that implementation of LED-FM on bleach pre-treated and concentrated sputum can significantly improve the diagnosis of smear-negative pulmonary tuberculosis. However, all scanty grade, positive smears by LED-FM need to be confirmed by reference culture method. |
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ISSN: | 2225-2002 2225-2010 |