Comparison of two bacteriophage tests and nucleic acid amplification for the diagnosis of pulmonary tuberculosis in sub-Saharan Africa
Abstract:SETTING: National reference laboratory in Zambia, a high-incidence setting with a high prevalence of HIV infection.
OBJECTIVE: To compare the performance of a commercial bacteriophage kit with a nucleic acid amplification kit and an ‘in-house’ bacteriophage method for rapid diagnosis of pulmonary tuberculosis (TB).
METHODS: Sputum specimens from suspected pulmonary TB cases were examined by direct fluorescence microscopy and culture on Löwenstein Jensen (LJ). In a blinded study, remaining samples were tested by AMTD and FASTPlaqueTB™ or an in-house bacteriophage assay. Two specimen decontamination protocols were investigated.
RESULTS: Microbial contamination of 40.4% was observed when using the FASTPlaqueTB kit specimen preparation protocol. When compared to culture on LJ, the sensitivity of the FASTPlaqueTB test was 20.7%. Implementation of a modified Petroff's decontamination protocol reduced contamination to 5.8% and the FASTPlaqueTB test detected 8/25 (32%) of culture-positive specimens. The sensitivity of AMTD and smear microscopy for these specimens were 64% and 48%, respectively. In a separate experiment the sensitivity of an in-house bacteriophage assay was 45.3% compared to 64.2% for AMTD and 45.3% for direct smear microscopy.
CONCLUSIONS: Additional analysis of sputum specimens by bacteriophage assay provided no advantage in this setting. For the rapid diagnosis of TB, AMTD offered improved sensitivity over direct smear microscopy.
Document Type: Regular Paper
Affiliations: 1: ZAMBART Project and Department of Microbiology and Pathology, University Teaching Hospital, Lusaka, Zambia 2: Chest Diseases Laboratory, Ministry of Health, Lusaka, Zambia 3: Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
Publication date: November 1, 2004
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