GLOBAL HEALTH | Addressing the world’s health challenges
21 October 2008
$2 Egg Beater May Help Diagnose Disease in Developing Countries
Device enables portable blood tests to be performed without electricity
Washington — Plastic tubing, tape and a $2 egg beater could be used to perform blood tests in the field, according to a report in the journal Lab on a Chip.
The portable apparatus requires no electrical power and could help diagnose diseases, such as hepatitis and tapeworm infections, in areas distant from centralized laboratories.
“This technique is simple and works remarkably well,” said Doug Weibel, a microbiologist at the University of Wisconsin-Madison.
Designed by George M. Whitesides and his colleagues at Harvard University, the modified egg beater is a substitute for bulky centrifuge equipment that costs hundreds of dollars and requires electricity to separate plasma from blood.
Isolating plasma in the field would reduce the time required to diagnose an infection and would increase access to patients located in remote areas and unable to travel to central health facilities, according to the report.
AN INEXPENSIVE, PORTABLE CENTRIFUGE
Medical diagnostics often rely on testing plasma, the liquid portion of whole blood. Plasma is obtained by spinning tubes of whole blood rapidly in a centrifuge, which separates molecules according to their densities — blood cells sink to the bottom while the liquid plasma remains on top. The presence of viruses and parasites, and the levels of clinically important molecules such as cholesterol can be determined using plasma.
To make an egg-beater centrifuge, researchers took a short stretch of plastic, polyethylene tubing (inner diameter 1.57 millimeters), filled it with whole blood and taped one end to an egg beater. Operating the egg beater at a “comfortable pace” for approximately 10 minutes separated plasma, according to the study.
Scientists used a simple, inexpensive paper-based test to measure cholesterol levels in plasma before and after adding known amounts of cholesterol to whole blood. The added cholesterol increased levels as expected, indicating that the plasma was isolated correctly.
Plasma isolated using the egg-beater method is good enough to use in tests to detect hepatitis B and cysticercosis (a parasitic disease) and probably could be used to detect other infectious diseases, according to the authors.
USING SCIENCE TO BENEFIT DEVELOPING NATIONS
One focus of the Whitesides Research Group is using science to benefit people in developing economies. Their goal is to develop diagnostic tools that are inexpensive, adaptable to local conditions and easily stored, transported and operated.
So far, they have developed an inexpensive and portable method for using antibodies to test for disease. This test can distinguish HIV-infected blood from uninfected blood.
For the egg-beater centrifuge, Whitesides purchased a $2.50 egg beater from a local grocery store in Cambridge, Massachusetts — a similar egg beater is sold throughout India for 105 rupees. The egg-beater centrifuge should reduce the burden on health care workers, who often are limited by insufficient supplies. Unlike expensive medical equipment, the egg-beater centrifuge is not an attractive target for thieves.
Researchers hope that this tool will enable further development of tests that rely on blood plasma.
“The objective was to separate [plasma] from blood using readily obtained materials in a resource-constrained environment,” said Whitesides. “The work opens eyes to new possibilities.”
