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Free Content Sensitivity and specificity of fluorescence microscopy for diagnosing pulmonary tuberculosis in a high HIV prevalence setting

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Abstract:

SETTING: Mulago Hospital, Kampala, Uganda.

OBJECTIVE: To evaluate the diagnostic performance of fluorescence microscopy (FM) for diagnosing pulmonary tuberculosis (TB) in a high human immunodeficiency virus (HIV) prevalence setting.

DESIGN: Consecutive in-patients with cough for >2 weeks submitted two sputum specimens for smear microscopy. Smears were examined by conventional light microscopy (CM) and FM. The performance of the two methods was compared using mycobacterial culture as a reference standard.

RESULTS: A total of 426 patients (82% HIV-infected) were evaluated. FM identified 11% more smear-positive patients than CM (49% vs. 38%, P < 0.001). However, positive FM results were less likely than positive CM results to be confirmed by culture when smears were read as either ‘scanty’ (54% vs. 90%, P < 0.001) or 1+ (82% vs. 91%, P = 0.02). Compared to CM, the sensitivity of FM was higher (72% vs. 64%, P = 0.005), and the specificity lower (81% vs. 96%, P < 0.001). In receiver operating characteristic analysis, maximum area under the curve for FM was obtained at a threshold of >4 acid-fast bacilli/100 fields (sensitivity 68%, specificity 90%).

CONCLUSION: Although FM increases the sensitivity of sputum smear microscopy, additional data on FM specificity and on the clinical consequences associated with false-positive FM results are needed to guide implementation of this technology in high HIV prevalence settings.

Keywords: HIV/AIDS; sensitivity and specificity; smear microscopy; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, California, USA; and Francis J Curry National Tuberculosis Center, San Francisco General Hospital, San Francisco, California, USA 2: Department of Medicine, Faculty of Medicine, Makerere University, Kampala, Uganda; and Uganda Ministry of Health, Kampala, Uganda 3: Makerere University–University of California San Francisco Research Collaboration, Kampala, Uganda 4: Department of Medicine, Faculty of Medicine, Makerere University, Kampala, Uganda 5: Uganda Ministry of Health, Kampala, Uganda 6: Uganda Ministry of Health, Kampala, Uganda; and Department of Medical Microbiology, Faculty of Medicine, Makerere University, Kampala, Uganda 7: Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA 8: Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, California, USA; and HIV/AIDS Division, University of California, San Francisco, California, USA

Publication date: 2009-09-01

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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