Validation of the Bleach Methods for the Diagnosis of Pulmonary Tuberculosis

Merid, Yared (2007) Validation of the Bleach Methods for the Diagnosis of Pulmonary Tuberculosis. Masters thesis, Addis Ababa University.

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Abstract

Bacteriological diagnosis of tuberculosis is largely dependent on direct microscopy of sputum smears. It is the most widely available diagnostic test, especially in developing countries where the other options are usually not practical due to the limited resources available. However, its sensitivity is not optimal when used in control programs, usually ranging from 8.8% to 46.4% in most African laboratories. The sensitivity of the technique is further undermined in areas with high HIV prevalence. If sensitivity could be improved, the method has the potential to become an even more valuable tool for National TB Control Programs. Treating the sputum with house bleach (NaOCl) has been reported to increase sensitivity of direct microscopy. Therefore, the aim of this study was to compare the diagnostic performance of the three different bleach methods reported so far: centrifugation, overnight sedimentation and short term bleach digestion (30 min), with conventional direct microscopy and validate against culture as a gold standard on a given group of specimens. This cross sectional study was conducted at Awassa Health Center and Bushulo Major Health Center in Awassa. Five hundred (500) consecutive new TB suspects presenting at the health facilities during July to December, 2006 were enrolled in the study. Direct smears were prepared and stained using Ziehl-Neelsen technique and specimens were decontaminated and inoculated onto Lowenstein-Jensen media for culture. The left over sputum samples were pooled, equal amount of bleach was added and then divided in three portions for the three bleach treatment techniques. Smears were prepared after centrifugation, overnight sedimentation and short term digestion. The direct and bleach treated smears were read blindly by two independent microscopists. Ten percent of the negative and 20% of all the positive smears were retained for quality control. Smears were graded using the WHO/IUATLD scale. Considering smears graded scanty (<10 Acid-fast bacilli per 100 fields) as negative, the direct smear was positive in 21%, short term digestion in 20%, overnight sedimentation in 23%, centrifugation in 31% and culture in 47%. The sensitivity of direct smear microscopy under the experimental condition was 41.9%. Among the bleach techniques, sensitivity was best for centrifugation (54.6%) followed by overnight sedimentation (43.7%) and short term digestion (38.9%). The bleach centrifugation method can clearly increase the sensitivity of smear microscopy and would thus be a useful tool to improve case detection in the National Tuberculosis Programme.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Tuberculosis, diagnosis, bleach methods, validation
Subjects:	Q Science > Q Science (General) Q Science > QR Microbiology
Divisions:	Africana
Depositing User:	Vincent Mpoza
Date Deposited:	21 Jun 2018 09:06
Last Modified:	21 Jun 2018 09:06
URI:	http://thesisbank.jhia.ac.ke/id/eprint/5349

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