24 Mar 2011
LED fluorescence microscopy is now recommended by the World Health Organization as the preferred technique for detecting the disease.
A robust, low-cost Carl Zeiss microscope based around a blue LED light source is set to become a major part of the global fight to control the spread of the killer lung disease tuberculosis (TB).
Since 2006, the World Health Organization (WHO) has used World Tuberculosis Day – March 24 – to highlight the global impact of TB. And following a review of the best techniques for detecting the disease, it is now recommending that LED fluorescence microscopy replaces the traditional Ziehl-Neelsen staining method.
Zeiss is a member of the WHO’s “Stop TB Partnership”, and has developed the “Primo Star iLED” microscope for TB diagnostics with the Foundation for Innovative Diagnostics (FIND). As part of that initiative, the German company is now selling the equipment to 74 countries that have a particularly high TB rate for a special price of €1250.
Silvia Zenner-Gellrich from the Biosicences Imaging division of Carl Zeiss MicroImaging in Göttingen told optics.org that the Primo Star equipment is far more robust and portable than a conventional fluorescence microscope, which would typically use a mercury lamp.
While mercury lamps are still useful in a laboratory setting because they provide such a broad spectrum, covering the biologically-important ultraviolet range, using a 455 nm high-brightness LED source instead means that the microscopes can be run on battery power. They are also much easier to handle, require no cooling, and have a much longer working lifetime – making the technology ideal for field laboratories and hospitals in the developing world.
Brighter emitters key
Zenner-Gellrich added that the development had only become possible in recent years because of the giant strides made by LED chip manufacturers in producing much brighter and more efficient emitters.
Zeiss launched the Primo Star iLED microscope in late 2008 (see optics.org's report at the time), but the uptake for TB diagnosis has been somewhat hampered – partly because the technique did not initially come with the explicit recommendation from WHO, and partly because it means that a different type of staining is required than clinicians are used to.
But with the new WHO recommendation and a move to educate clinicians using the tool, Zenner-Gellrich is hopeful that uptake will now accelerate. In a review of the evidence for the different diagnostic approaches that it carried out last year, WHO concluded:
“Results showed equivalent accuracy of LED microscopy to international reference standards, improved sensitivity over conventional Ziehl-Neelsen microscopy, and qualitative, operational and cost advantages of LED relative to both conventional fluorescent and Ziehl-Neelsen microscopy.”
“WHO recommends that conventional fluorescent microscopy be replaced by LED microscopy. The switch to LED microscopy should be carried out through carefully phased implementation plans at country level, using LED technologies that meet WHO specifications.”
TB is one of the world’s major killer diseases, and typically affects young adults. According to WHO’s latest figures, in 2009 around 4700 people died each day as a result of TB (equivalent to 1.7 million per year). And although the death rate has fallen by 35% since 1990, there were still 9.4 million new cases of the disease during 2009.
WHO’s targets include halving the number of deaths from TB globally by 2015 – in comparison with the level in 1990 – and the organization believes that 5 million lives can be saved within the next five years under its global plan to combat the disease.
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