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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2371

Authors: Nebiyu, Gizaw
Advisors: Solomon G/Selassie (MD, MSc)
Kassu Desta (BSc, MSc)
Kassu Desta (BSc, MSc)
Keywords: Mycobacteria Growth Indicator Tube(MGIT)
Mycobacterium tuberculosis
Sodium Hypochlorite (Household bleach)
Auramine O/Phenol
Neelsen (ZN)
Light Emitting Diode Fluorescent Microscopy (LED-FM)
Copyright: Apr-2011
Date Added: 3-May-2012
Publisher: AAU
Abstract: Conventional light microscopy using Ziehl-Neelsen (ZN) stained smears prepared directly from sputum specimens is the most widely available test for diagnosis of tuberculosis (TB) in resource-limited settings. However, a major shortcoming of conventional microscopy is its low sensitivity compared with culture. A cross-sectional study in the outpatient departments of St. peter’s TB specialized hospital in Addis Ababa, Ethiopia from May, 2010 to December, 2010 was conducted to compare the diagnostic value of the combination of bleach and light emitting diode fluorescent microscopy (LED-FM) against mycobacterial culture in the diagnosis of pulmonary tuberculosis (PTB) Adult patients with chronic cough, weight loss, sweats , fever, hemoptysis, chest pain with radiographic findings without treatment or on anti-TB chemotherapy were included in the study. Three consecutive sputum specimens from patients who fulfilled entry criteria were processed. Direct smear were prepared and stained using auramine phenol and Ziehl Neelsen techniques. Concentrated slides using bleach were stained by auramine-phenol method with culture on MGIT media as the gold standard. Capilia TB Assay method were used to identify M. tuberculosis. Three hundrades and fifty three sputa were processed. The sensitivity, specificity, positive and negative predictive values achieved with direct fluorescent microscopy compared to culture were 59.7%, 98.3%, 94.4% and 83.6% respectively. The correlation between direct fluorescent microscopy and culture as gold standard method showed statistical significance (χ2 = 159.78, P < 0.001).Concentration of sputum with bleach significantly increased auramine/phenol smear sensitivity by 72.8%, a 13.1% incremental yield (χ2 = 197.8, P < 0.0001). A comparison of direct ZN and FM smear results showed that, direct FM sensitivity was significantly higher than direct ZN microscopy (59.7% vs 41.2%, difference 18.5%, χ2 = 159.3, CI 30.2 – 249.8, P<0.0001) but FM specificity was slightly lower (98.3% vs 100%). Sputum processing with bleach increased FM smear sensitivity by 31.6%, from 41.2% to 72.8%, which was remained significantly higher as compared with direct ZN microscopy (χ2 = 204.17, 95% CI = 37.64 – 209.2 P<0.0001) but FM specificity slightly decreased than direct ZN, from 97% to 100%. In this study it was shown that LED FM has correspondence with culture with decreasing number of bacilli. Low scanty results in fluorescence microscopy correlated more with culture than low scanty results found with the Ziehl-Neelsen technique. Symptoms like fever, cough and chest ix pain were the common clinical findings among patient with suspected of having tuberculosis in our study. Weight loss was highly associated with development of PTB in both direct and concentrated flourochrome stained methods. Abnormal X-ray finding and positivity with both direct and concentrated fluorescent microscopy were highly associated. Therefore, the Auramine fluorochrome stain positive cases do not necessarily require to do X-ray examination as it saves time and money. According to the present study, combination of bleach and LED based fluorescent microscopy is sensitive and specific, easy to perform, inexpensive, rapid, diagnostic test for pulmonary tuberculosis.
URI: http://hdl.handle.net/123456789/2371
Appears in:Thesis - Medical Microbiology

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