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A durable, lightweight and low-cost microscope that can be carried in a backpack is as effective in helping diagnose tuberculosis (TB) as a standard laboratory microscope costing thousands of dollars, a preliminary study by Iranian and US scientists has found.

The Global Focus microscope weighs one kilogram and costs around US$240, compared with laboratory-grade microscopes, which can weigh around 10kg and cost up to US$2,000.

The backpack microscope provides up to 1,000x magnification, more than sufficient to spot TB bacilli according to the study, published in PLoS ONE earlier this month (4 August).

Co-author Ahmad Bahrmand, former TB laboratory director at the Pasteur Institute of Iran told SciDev.Net the microscope is "portable, cheap and easy to work with".

"There is a strong need for [point-of-care] TB diagnosis," he added.

Bahrmand provided and prepared more than 60 samples from 19 patients collected in rural areas of Iran — samples he and his co-authors said are representative of those that would likely be evaluated in the field with the microscope.

They compared TB diagnoses made with the Global Focus microscope with those by a standard laboratory microscope, and found that evaluations of the samples as positive or negative agreed in all except one case.

The backpack microscope was developed by Andrew Miller, now a medical device designer, as part of a student project for the Beyond Traditional Borders programme at Rice 360˚: Institute for Global Health Technologies of Rice University, United States. He told SciDev.Net: "Not only is [the microscope] small and portable, but it also uses AA batteries and a flashlight, so it can operate without electrical supplies, and it's durable – both rugged and easy to repair."

The microscope will be sent out to nine clinical sites in Africa and Latin America for further feedback.

Miller said that the next step is to look for partners for appropriate distribution with training programmes. He added that twenty prototypes would be in field studies later this year in locations that are yet to be finalised.

"There has been interest from scientists and clinicians in a variety of places, including Angola and South America," said Robert Miros, chief executive officer of 3rd Stone Design in California, which is manufacturing the prototypes for developing country use.

"[This design] lends itself to smaller-scale manufacture. You don't necessarily need an order for a hundred thousand for good prices," Miros told SciDev.Net.

Link to full paper in PLoS ONE

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