Diagnosis of Phenylketonuria

A PKU test is conducted a day or two after the baby is born. In the test, a nurse or lab technician collects a few drops of blood from the baby's heel or the bend in the baby's arm using a needle or lancet. A laboratory tests the blood sample for certain metabolic disorders, including PKU. The test isn't done before the baby is 24 hours old or before the baby has ingested some protein in the diet for accuracy in results. If the baby isn't delivered in a hospital or are discharged soon after the birth, a newborn screening with pediatrician or family doctor is compulsory.

Babies may also have additional tests to confirm the diagnosis, including more blood tests and urine tests. The parent and baby may also undergo genetic testing to identify any gene mutation leading to PKU.

A simple method utilized to detect phenylketonuria was the Gunthrie Test which employs the use of a bacterial inhibition assay. This bacterial requires phenylalanine for growth. The agar also contains a nonmetabolizable competitive inhibitor set at a certain concentration that the amount of phenylalanine in normal will not support noticeable growth.

Reference

• Phenylketonuria: Tests and diagnosis - MayoClinic.com. 2013. Phenylketonuria: Tests and diagnosis - MayoClinic.com. [ONLINE] Available at: http://www.mayoclinic.com/health/phenylketonuria/DS00514/DSECTION=tests-and-diagnosis. [Accessed 13 January 2013].
• Guthrie test definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms. 2013. Guthrie test definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms. [ONLINE] Available at: http://www.medterms.com/script/main/art.asp?articlekey=11390. [Accessed 17 January 2013].