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Phenylalanine concentrations are routinely screened in newborns by the neonatal heel prick (Guthrie test), which takes a few drops of blood from the heel of the infant. Standard phenylalanine concentrations in unaffected persons are about 2-6mg/dl (120–360 μmol/L) phenylalanine concentrations in those with untreated hyperphenylalaninemia can ...
Directed by screening newborn for elevated plasma levels of phenylalanine. The normal level of phenyl alanine in plasma is 1–2 mg/dl and in PKU, it normally ranges between 20–65 mg/dl. The main test for confirmation of PKU is the Guthrie test, which is a Bacillus subtilis Bioassay. [citation needed]
This test can reveal elevated phenylalanine levels after one or two days of normal infant feeding. [11] [12] If a child is not diagnosed during the routine newborn screening test and a phenylalanine-restricted diet is not introduced, then phenylalanine levels in the blood will increase over time.
The test uses the growth of a strain of bacteria on a specially-prepared agar plate as a sign for the presence of high levels of phenylalanine, phenylpyruvate, and/or phenyllactate. The compound B-2-thienylalanine will inhibit the growth of the bacterium Bacillus subtilis (ATCC 6051) on minimal culture media. If phenylalanine, phenylpyruvate ...
Infants with PKU appear normal at birth, but are unable to metabolize the essential amino acid phenylalanine, resulting in irreversible intellectual disability. In the 1960s, Robert Guthrie developed a simple method using a bacterial inhibition assay that could detect high levels of phenylalanine in blood shortly after a baby was born.
Reference ranges (reference intervals) for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples. Reference ranges for blood tests are studied within the field of clinical chemistry (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the ...
Here, his test correctly identified all patients known to have PKU and also four who had previously been undiagnosed. [1] In 1961, Guthrie and his lab started screening infants for PKU, a project that quickly expanded. In two years, they had tested 400,000 American newborns, and diagnosed 39 with PKU.
Conditions justifying newborn screening for any disorder include (1) a simple test with an acceptable sensitivity and specificity, (2) a dire consequence if not diagnosed early, (3) an effective treatment if diagnosed, and (4) a frequency in the population high enough to justify the expense. In the last decade more states and countries are ...