Phenylketonuria was first discovered in the 1930's by a doctor in Norway, Asbjorn Folling. He was studying the condition in two small children with severe mental retardation, and found high levels of phenylalanine in their urine. This lead him to conclude that they were not properly breaking down the amino acid.
The first diet for children diagnosed with PKU comes around in England in the 1950's. The basic idea was to use a reduced phe milk to feed to the babies during the first six months. This showed great improvements in the mental function of PKU babies versus those who did not receive this treatment. At this point in history, the condition was found by testing the urine of newborns (the "wet diaper test") for high levels of phe, an indication of phenylketonuria. However, this test is not very accurate.
Enter Dr. Robert Guthrie, an American doctor whose fifteen month old niece was diagnosed with PKU. Around this time, PKU was being treated by diets low in phe, thanks to the work of Horst Bickel. The problem was that methods of identifying PKU at this time were not effective in catching the condition early enough.
Dr. Guthrie pioneered what would become known as the Guthrie test. Using blood samples and inhibiting bacteria growth using a phenylalanine antagonist, his test would allow the bacteria to grow if high levels of phenylalanine were present in the blood.
Initially, the tests were done on patients with known PKU as well as some who were undiagnosed. Once the tests were shown to be successful, they started implementing them in new born babies. In two years 400,000 babies were tested in the United States and 39 were diagnosed with PKU. Today, the test is used all over the world to screen newborns, with many countries requiring it by law.
