First home-testing device for phenylketonuria (PKU) patients

Home-testing kits have made it easier for diabetics and hypertension patients to track their conditions, but such self-monitoring hasn’t been possible for people with phenylketonuria (PKU). Georgia Tech researchers and an Atlanta start-up company hope to change that by introducing the first home-testing device for PKU patients.

PKU is a genetic metabolic disorder in which the body lacks a liver enzyme (phenylalanine hydroxlase) needed to process phenylalanine, an essential amino acid, into another amino acid (tyrosine) used by the body. Left unconverted, excessive amounts of phenylalanine in the bloodstream are toxic to brain tissue and the central nervous system; if untreated in newborns, PKU can cause brain damage and mental retardation.

There is no drug that can cure PKU. It can only be treated through diet. Because phenlylalanine is a component of proteins, patients must follow a strict low-protein diet, avoiding meat, fish, eggs, poultry, dairy and soy products as well as products containing the artificial sweetener aspartame. “When phenylalanine levels become too high, PKU patients can suffer movement disorders, such as tremors, seizures and hyperactivity,” explains Jeff Sitterle, chief scientist at the Georgia Tech Research Institute (GTRI) and project director for the PKU testing device.

Blood-testing requirements vary depending on the severity of a patient’s condition, but frequent monitoring is especially important for children. The goal is to maintain phenylalanine levels in the blood between 2 and 10 milligrams per deciliter. Pregnant women must also be careful, for if phenylalanine levels get too high, it can affect development of the fetus.

In the United States, there are about 120 centers where PKU monitoring is conducted. That means frequent testing can be costly and inconvenient for patients who must travel long distances to reach a center.

Because PKU is considered an “orphan disease” – one that affects a small sector of the population – large pharmaceutical companies haven’t pursued a home test for the disease.

“Incidence of PKU varies around the world,” says Richard Shunnarah, president of Atlanta-based MetGen Inc., which is developing blood-monitoring devices for metabolic genetic disorders. In the United States, PKU occurs in about one in 10,000 births, but varies from a low of 1 in 100,000 births in Japan to a high of 1 in 2,600 births in Turkey, he adds.

A 20-year veteran of the clinical nutrition industry, Shunnarah launched MetGen in 2002 and approached Georgia Tech for assistance in developing a PKU home test. Sitterle, whose great-niece suffers from the disease, quickly recognized the significance of the project.

“PKU patients can keep records of what they eat, but there’s no way to know what their blood levels are without frequent testing,” Sitterle says. “A home test will help patients understand how their bodies react to food.”

What’s more, the testing device will store data, providing a history for doctors to review during patients’ routine checkups. “That gives doctors a true trend picture, rather than blood levels that might have resulted from patients making a sudden effort to stick to their diet prior to the checkup,” Sitterle adds.

An interdisciplinary project, GTRI engineers have built the electronics for the PKU home test while Sheldon May, a Regents professor in Georgia Tech’s School of Chemistry and Biochemistry, has developed a special reagent strip for the device, assisted by graduate student Veronica de Silva.

Similar to a blood-glucose home test, a PKU patient pricks his or her finger and then places a drop of blood on the reagent strip inserted in the testing device. Phenylalanine in the blood causes a reaction to take place on the test strip. Then electronics in the device calculate the rate at which the test strip absorbs a specific color of light. This rate indicates the level of phenylalanine in the blood.

“That may sound simple, but it actually requires thousands of measurements and a mathematical algorithm to pinpoint the right section of data to evaluate,” explains Tim Strike, associate head of the Technology Application Branch in GTRI’s Electronic Systems Laboratory.

One of the project’s requirements was to keep consumer costs down, which researchers achieved by using off-the-shelf components. “Because PKU is an orphan disease, we wanted a device that would be affordable to produce in smaller numbers,” says project collaborator Ron Bohlander, director of GTRI’s Commercial Product Realization Office (CPRO).

Another challenge was user-friendliness – important because PKU patients range in age and educational levels, researchers note. That meant keeping display menus and terminology simple, and reducing the number of steps required to operate the device.

“If you have too many steps to follow, it can be confusing for new users – and downright irritating when you use it on a regular basis,” Strike adds. “We wanted to make this as easy as buying a soft drink from a machine.”

This past summer, scientists at Emory University – where Georgia’s only PKU treatment center is located – conducted tests to validate the technology. Since then, Georgia Tech has been helping MetGen find manufacturers for the chemical strip and electronic device. MetGen hopes to win FDA approval by the end of this year and begin marketing the PKU home test in early 2005.

Earlier this year, MetGen received an $85,000 grant from the Georgia Research Alliance’s (GRA) Innovation Fund, which fosters partnerships between Georgia companies and the state’s research universities.

“GRA’s support was instrumental,” says Shunnarah, who also hopes to develop in-home tests for other rare metabolic genetic disorders. “Without GRA’s assistance, we would have had to seek outside investors, and that would have been difficult due to the size and uniqueness of this market.

“This may be a small market,” Shunnarah adds, “but real-time feedback on blood levels will make a significant impact on the lives of PKU patients. In addition, dietary compliance will be enhanced, enabling healthcare professionals to provide instantaneous recommendations to patient’s diets.”


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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