Abstract
BackgroundDespite 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.ObjectiveThis study aimed to evaluate the diagnostic performance of LED-FM for smear-negative pulmonary tuberculosis in Ethiopia.MethodsA 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).ResultsOf 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).ConclusionThis 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.
Highlights
Ethiopia is among the 30 highest-burden countries for tuberculosis, tuberculosis-HIV coinfection and multidrug-resistant tuberculosis in the world.[1]
We aimed to evaluate the diagnostic performance of light-emitting diode fluorescent microscopy (LED-fluorescence microscopy (FM)) in bleach pre-treated and concentrated sputum specimens for the diagnosis of smear-negative pulmonary tuberculosis in Ethiopia
The effect of bleach pretreatment and http://www.ajlmonline.org concentration in the diagnosis of smear-negative tuberculosis will be evaluated. This was not done in the current study. Of those patients found to have a negative result in three consecutive sputum examinations with ZN, a significant proportion (10.8%) had a positive result using light-emitting diode (LED)-FM after bleach processing and centrifugation
Summary
Ethiopia is among the 30 highest-burden countries for tuberculosis, tuberculosis-HIV coinfection and multidrug-resistant tuberculosis in the world.[1]. Sputum smear-positive cases are more infectious than smear-negatives, studies have reported that 17% of tuberculosis transmissions were due to sputum smear-negative but culture-positive cases.[3] smear-negative pulmonary tuberculosis cases are associated with longer health service delays due to delayed diagnosis. Such delays in diagnosis may delay initiation of treatment, and further tuberculosis transmission may occur.[4,5]. The World Health Organization (WHO) has recommended Xpert MTB/RIF as the initial http://www.ajlmonline.org. 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
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