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Validation of bleach-treated smears for the diagnosis of pulmonary tuberculosis

Merid, Y., Yassin, Mohammed A., Yamuah, L., Kumar, R., Engers, H. and Aseffa, A. (2009) 'Validation of bleach-treated smears for the diagnosis of pulmonary tuberculosis'. International Journal of Tuberculosis and Lung Disease, Vol 13, Issue 1, pp. 136-141.

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Abstract

SETTING: Health centres in Awassa, southern Ethiopia.
DESIGN: Consecutive patients visiting health centre laboratories for the evaluation of suspected pulmonary tuberculosis (TB) between June and September 2006 were investigated. On-the-spot, morning and second on-the-spot sputum samples were pooled for each patient. Direct smears were stained with hot Ziehl-Neelsen (ZN) technique and aliquots cultured for mycobacteria on Lowenstein-Jensen media. The remaining sputum was treated with household bleach, aliquoted and processed with short-term digestion, centrifugation and sedimentation techniques, and stained with ZN.
RESULTS: Acid-fast bacilli were detected in respectively 126 (25%), 141 (28%), 169 (34%) and 198 (40%) of the 497 pooled sputum samples processed by the direct, short-term, sedimentation and centrifugation techniques (P < 0.001). The sensitivity of the direct, short-term, sedimentation and centrifugation techniques was respectively 51.1%, 53.2%, 57.6% and 63.6%. The difference between the direct smear and centrifugation (P < 0.001) or sedimentation (P < 0.005) methods was significant. The specificity of the direct, short-term digestion, sedimentation and centrifugation techniques was respectively 97%, 93%, 86.5% and 80.8%.
CONCLUSIONS: Bleach treatment of sputum and centrifugation significantly improves the sensitivity of smear microscopy for the diagnosis of TB in a health centre in a high TB burden area. It is more sensitive, but possibly less specific, than other bleach methods.

Item Type: Article
Uncontrolled Keywords: acid-fast bacilli microscopy bleach pooled sputum validation scanty afb smears acid-fast bacilli improved sensitivity sputum specimens mycobacterium-tuberculosis developing-countries direct microscopy culture hiv centrifugation
Subjects: QY Clinical Pathology > Diagnostic Tests > QY 120 Sputum
WF Respiratory System > Tuberculosis > WF 220 Diagnosis. Prognosis
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WF Respiratory System > WF 100 General works
WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WF Respiratory System > Tuberculosis > WF 300 Pulmonary tuberculosis
WF Respiratory System > Tuberculosis > WF 215 Pathology
Faculty: Department: Groups (2002 - 2012) > Child & Reproductive Health Group
Depositing User: Pauline Anderson
Date Deposited: 12 Mar 2010 15:03
Last Modified: 06 Feb 2018 12:59
URI: http://archive.lstmed.ac.uk/id/eprint/326

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