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Microbiological validation of smear microscopy after sputum digestion with bleach; a step closer to a one-stop diagnosis of pulmonary tuberculosis

Lawson, Lovett, Yassin, Mohammed A., Ramsay, Andrew, Olajide, I., Thacher, T. D., Davies, P. D. O., Squire, Bertie ORCID: and Cuevas, Luis ORCID: (2006) 'Microbiological validation of smear microscopy after sputum digestion with bleach; a step closer to a one-stop diagnosis of pulmonary tuberculosis'. Tuberculosis, Vol 86, Issue 1, pp. 34-40.

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Background: Smear microscopy is relatively insensitive for the diagnosis of TB. The digestion of sputum with household bleach prior to smear preparation has been reported to improve its sensitivity. This method has not been validated.
Methods: Seven hundred and fifty six patients with symptoms suggestive of pulmonary TB (PTB) were asked to submit 3 sputum specimens for direct microscopy. One specimen was selected at random for culture and another specimen was digested to prepare a further smear. The WHO case definition (>= 2 positive smears or one positive smear and positive culture) was used to compare the sensitivity and specificity of the smears.
Findings: Four hundred and fifty five (60%) patients were culture-positive. Of these, 235 (31%) had "definite" PTB and 223 (29%) "very likely" PTB (smear-negative, culture-positive). The WHO case definition identified 51% (235/458) of the patients with "definite" or "very likely" PTB. One digested smear detected 219 (93%) of the 235 patients with "definite" PTB and 10 patients with "very likely" PTB (sensitivity (95%Cl) 50% (45-55%); specificity 99% (97-100%)). The positive and negative predictive values for one digested smear were 98% (95-99%) and 56% (52-60%) respectively, which were not different (p > 0.5) to the WHO case definition (100% and 57%, respectively).
Interpretation: One bleach-digested smear is as sensitive and specific as the WHO case definition for the diagnosis of PTB. (c) 2005 Etsevier Ltd. All rights reserved.

Item Type: Article
Uncontrolled Keywords: tuberculosis diagnosis ziehl-neelsen sputum smear digestion bleach nigeria acid-fast bacilli developing-countries sensitivity quality
Subjects: QY Clinical Pathology > Diagnostic Tests > QY 120 Sputum
QY Clinical Pathology > QY 4 General works
WF Respiratory System > WF 140 Diseases of the respiratory system (General)
WF Respiratory System > WF 20 Research (General)
WF Respiratory System > Tuberculosis > WF 200 Tuberculosis (General)
WF Respiratory System > Tuberculosis > WF 205 Epidemiology
WF Respiratory System > Tuberculosis > WF 220 Diagnosis. Prognosis
WF Respiratory System > Tuberculosis > WF 300 Pulmonary tuberculosis
Faculty: Department: Groups (2002 - 2012) > Child & Reproductive Health Group
Groups (2002 - 2012) > Clinical Group
Digital Object Identifer (DOI):
Depositing User: Sarah Lewis-Newton
Date Deposited: 22 Feb 2011 11:23
Last Modified: 17 Jul 2020 10:58


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