Home testing for rare disease.

• Position: Genetic Disorders

Home-testing kits have made it easier for diabetics and hypertension patients to track their conditions, but such self-monitoring has not been possible for people with phenylketonuria (PKU). Researchers at the Georgia Institute of Technology, Atlanta, 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 hydroxylase) needed to process phenylalanine, an essential amino acid, into another amino acid (tyrosine). 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.

PKU only can be treated through diet. Because phenylalanine 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 and project director for the PKU testing device.

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