Systematic Review Series on TB Diagnostics

Sputum Microscopy

photo credit: Jan van den Hombergh, Lung Health Image Library, World Lung Foundation, 2003

The vast majority of tuberculosis (TB) patients live in low- and middle-income countries, where the diagnosis of TB disease relies primarily on identification of acid-fast bacilli on sputum smears using a conventional light microscope. In these countries, most laboratories use smears of unconcentrated sputum (direct smears) with Ziehl-Neelsen (ZN) staining. Microscopy is fast, simple, inexpensive, widely applicable, and highly specific for M. tuberculosis in TB endemic countries and identifies the most infectious patients. However, microscopy has known limitations, in particular modest and variable sensitivity. Moreover, sensitivity is limited for extrapulmonary and other forms of paucibacillary disease (e.g., pediatric and HIV-associated TB). As part of a project commissioned by the World Health Organization's Special Programme for Research and Training in Tropical Diseases (TDR) and the Foundation for Innovative New Diagnostics (FIND), researchers conducted a series of systematic reviews to determine the strength of existing evidence, identify knowledge gaps, and define a research agenda for microscopy.

1. Sputum processing methods to improve the sensitivity of smear microscopy for tuberculosis: a systematic review
   Steingart KR, Ng V, Henry M, Hopewell PC, Ramsay A, Cunningham J, Urbanczik R, Perkins MD, Aziz MA, Pai M
   Lancet Infect Dis 2006;6:664-74
   [download abstract]
    
2. Fluorescence versus conventional sputum smear microscopy for tuberculosis: a systematic review
   Steingart KR, Henry M, Ng V, Hopewell PC, Ramsay A, Cunningham J, Urbanczik R, Perkins M, Aziz MA, Pai M
   Lancet Infect Dis 2006;6:570-81
   [download abstract]
    
3. Yield of serial sputum specimen examinations in the diagnosis of pulmonary tuberculosis: a systematic review
   Mase SR, Ramsay A, Ng V, Henry M, Hopewell PC, Cunningham J, Urbanczik R, Perkins MD, Aziz MA, Pai M
   Int J Tuberc Lung Dis 2007 May;11(5):485-95
   [download abstract]
    
4. Fluorescence microscopy for tuberculosis diagnosis - Authors' reply
   Steingart KR, Ramsay A, Pai M
   Lancet Infect Dis 2007;7(4):239-240
    
5. Optimizing sputum smear microscopy for the diagnosis of pulmonary tuberculosis
   Steingart KR, Ramsay A, Pai M
   Expert Rev Anti Infect Ther 2007;5(3):327-331

    

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