Neonatal heel prick
The Guthrie test (after Robert Guthrie, 1916-1995 ) is an important part of the screening tests in the newborn. He was at date of birth to the 5th day of life in premature infants around the 10th day of life and is used for early detection of certain congenital metabolic disorder phenylketonuria. Because of error sources, he has been replaced in Germany in most hospitals by direct methods of determination. In Switzerland, the United States, the Netherlands and Belgium, he is still in use.
History
The test was developed by Robert Guthrie in the early 1960s and 1963, first introduced in the United States of America. In Germany, the test was first introduced in 1966 in North Rhine -Westphalia. The first tests were then carried out in hygienic - bacteriological Landesuntersuchungsamt in Dusseldorf, headed by Edip Önöz.
Disambiguation
When Guthrie test is historically the prototype of a screening examination in the neonatal period. In colloquial usage, the term has therefore widely naturalized as a generic term for all screening tests performed in the newborn. But in the actual sense it denotes only the below described, developed by Robert Guthrie and imported investigation.
Method
From the heel of the newborn, blood is dropped on a filter paper card and sent, after drying in an appropriate laboratory. There discs are punched out of a defined size and applied to a medium, which was inoculated with Bacillus subtilis ( ATCC 1651). The effect of the inhibitor present in the culture medium (2- thienylalanine ) is repealed by the presence of phenylalanine. Growth of the bacterial culture to the blood sample around suggesting increased phenylalanine and the size of the bacteria even at the approximate concentration Court the amino acid.
Sources of error
Since it was a biological detection method, it is subject to many sources of error. The concentration of phenylalanine is highly dependent on the amount of food consumed in the first days of life. Was this too low, below the detection limit of the Guthrie test even in the presence of this disorder of phenylalanine in the studied sample. Similarly, treatment with an antibiotic to inhibit bacterial growth in general, and thus lead to false-negative results in the newborn, which nevertheless had a disorder of Phenylalaninstoffwechsels. The Guthrie test is no longer performed in Germany, after much more sensitive direct detection methods have been developed for the phenylalanine concentration. In Switzerland, the Guthrie test has been replaced by tandem mass spectrometry (MS / MS) since 2005.