The neonatal heel prick or Guthrie test is a common procedure for taking a blood sample from the heel of newborn infants. A pinprick puncture is made in the heel of the infant's foot, and blood from the foot is soaked into pre-printed collection cards known as Guthrie cards.
The blood samples can be used for a variety of genetic tests, including:
- Thyroid stimulating hormone (TSH) to detect hypothyroidism and hence prevent cretinism.
- Trypsin to detect cystic fibrosis.
- Detection of phenylketonuria, an enzyme deficiency that can impair brain development.
Other potential tests include:
- A test for galactosemia
It is recommended that the screening test be performed when the infant is between 48 and 72 hours of age. False positives and negatives can sometimes occur when the screening tests are performed before 48 hours.
With genetic tests becoming more common, a wide variety of tests may use the blood drawn by this method. Many neonatal units (SCBUs) now use this method to carry out the daily blood tests (blood count, electrolytes) required to check the progress of ill neonates.
In the UK, the NHS test for:
- Hypothyroidism
- Cystic fibrosis
- Phenylketonuria (PKU)
- Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD)
- Sickle-cell disease
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And rich men grown to be poor again,
And I am running to Paradise;
And many a darling wit’s grown dull
That tossed a bare heel when at school,
Now it has filled an old sock full....”
—William Butler Yeats (1865–1939)
“Taint not thy mind, nor let thy soul contrive
Against thy mother aught. Leave her to heaven,
And to those thorns that in her bosom lodge
To prick and sting her.”
—William Shakespeare (1564–1616)