Home » Everything About PKU Test, PKU Glossary

What is PKU Test?

PKU (phenylketonuria) test is a newborn screening test designed to measure a level of phenylalanine (Phe) – an amino acid that is needed for normal growth and development – in baby’s body. Lack of enzyme that changes phenylalanine into another amino acid – called tyrosine – can increase the levels of phenylalanine in the blood and subsequently can cause serious brain damage or intellectual disability.

How it’s done

The procedure is pretty straightforward – the blood is collected from baby’s heal, usually within 48 hours after birth, and then is sent to a laboratory.

Types of PKU tests

Basically, there are three main PKU screening methods:

 1. Guthrie test – developed by an American bacteriologist and physician Robert Guthrie who simplified the PKU detection procedure in 1961.

2. Fluorescence spectroscopy – screening method in which a fluorometer analyzes fluorescence from a blood sample.

3. Tandem mass spectrometry – the most reliable PKU screening method which measure the weight of molecules in blood. The results are presented in a graph (mass spectrum).

The results

If the phenylalanine content in blood does not exceed 1-2 mg/dL, this is a clear sign that a child doesn’t have PKU. On the other hand, if this content is higher, the child will have to be on a low protein diet for the rest of his/hers life. If a newborn child is diagnosed with PKU, it is very important that he/she starts with the diet program as soon as possible.

Did you know?

Did you know that all the newborns since 1970s’ have had at least one (PKU) test done in their life? Most of the developed countries started to organize neonatal screenings from 1966. By the late 1960’s and early 1970’s, neonatal screenings became medical standard in hospitals across the USA.

Want to learn more?


“The PKU Paradox: A Short History of a Genetic Disease” by Diane B. Paul and Jeffrey P. Brosco.

“Robert Guthrie–The Pku Story: Crusade Against Mental Retardation” by Jean Holt Koch.

“Low Protein Cookery for Phenylketonuria” by Virginia E. Schuett.

“Low Protein Food List for PKU” by Virginia E. Schuett.

“Low Protein Bread Machine Baking for PKU” by Virginia E. Schuett.

Share/Bookmark this!

Leave a reply

Add your comment below, or trackback from your own site. You can also subscribe to these comments via RSS.

Be nice. Keep it clean. Stay on topic. No spam.

You can use these tags:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

This is a Gravatar-enabled weblog. To get your own globally recognized avatar, please register at Gravatar.


Recent Posts