Newborn screening !

A few drops of heel blood detect treatable diseases before they cause harm, such as congenital hypothyroidism and PKU.

Updated 2026-11-01

Key facts

It looks for diseases that are serious, treatable and silent at birth: early treatment prevents intellectual disability, metabolic crises or death.
Classics: congenital hypothyroidism (TSH), phenylketonuria (phenylalanine), galactosaemia, congenital adrenal hyperplasia (17-OH-progesterone), cystic fibrosis (immunoreactive trypsinogen), haemoglobinopathies, biotinidase deficiency.
Tandem mass spectrometry detects many amino acid, organic acid and fatty acid oxidation defects (acylcarnitines, as in MCAD deficiency) in a single sample.
A positive result is a suspicion: it is always confirmed with diagnostic tests.
In Colombia screening for congenital hypothyroidism has been mandatory for years, and regulation has extended newborn screening to more diseases.

Sample: heel blood (or cord blood for TSH in some programmes) on filter paper, ideally after 24–48 hours of life and after feeding has started.
Why timing matters: before 24 hours phenylalanine may not have risen yet (false negative) and TSH has a normal surge at birth (false positive).
Phenylketonuria: phenylalanine builds up for lack of phenylalanine hydroxylase (or BH4); a low-phenylalanine diet from the first weeks prevents brain damage.
Congenital hypothyroidism: a high TSH (or low T4) identifies newborns who, treated with levothyroxine in the first weeks, develop normally.
Classic galactosaemia: GALT deficiency builds up galactose-1-phosphate; removing lactose prevents liver failure, E. coli sepsis and cataracts.
Other newborn tests: hearing screening and pulse oximetry for critical congenital heart disease.
Premature, transfused or parenterally fed babies can give false results and need a repeat sample.

Also called: Neonatal screening, Heel-prick test, Newborn metabolic screening

A programme's value depends on follow-up: reaching the family, confirming the diagnosis and starting treatment in time.
A normal screen does not exclude disease if the baby develops matching symptoms.
Parents can receive genetic counselling when an autosomal recessive disease is confirmed.

Think of the answer, then tap the question to see it.

What makes a disease suitable for newborn screening?

Being serious, silent at birth, detectable with a reliable test and treatable, so that early treatment changes its course.

Why is the sample ideally taken after 24–48 hours?

Earlier, phenylalanine may not have risen and TSH has a normal surge at birth, giving false negatives and positives.

Which technique detects many inborn errors in a single blood spot?

Tandem mass spectrometry, which measures amino acids and acylcarnitines.

What does a positive screen mean?

A suspicion that must be confirmed with diagnostic tests before the disease is established.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Newborn screening tests: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Newborn Screening: MedlinePlus (MedlinePlus, US National Library of Medicine, 2026); Phenylketonuria (PKU) Screening: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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