[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Newborn screening

[Biochemistry](https://durgical.com/en/biochemistry/) · Topic

# 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.

## In detail

- 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

## Clinical notes

- 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.

## Related conditions

- [Phenylketonuria (PKU)](https://durgical.com/en/conditions/phenylketonuria/)
- [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/)
- [Classic galactosaemia](https://durgical.com/en/conditions/classic-galactosaemia/)
- [Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency](https://durgical.com/en/conditions/medium-chain-acyl-coa-dehydrogenase-deficiency/)
- [Sickle cell disease](https://durgical.com/en/conditions/sickle-cell-disease/)
- [Maple syrup urine disease](https://durgical.com/en/conditions/maple-syrup-urine-disease/)

## Related

- [Phenylalanine hydroxylase (PAH)](https://durgical.com/en/biochemistry/enzymes/phenylalanine-hydroxylase/)
- [Medium-chain acyl-CoA dehydrogenase (MCAD)](https://durgical.com/en/biochemistry/enzymes/medium-chain-acyl-coa-dehydrogenase/)
- [Galactose-1-phosphate uridylyltransferase (GALT)](https://durgical.com/en/biochemistry/enzymes/galactose-1-phosphate-uridylyltransferase/)
- [Glucose-6-phosphate dehydrogenase (G6PD)](https://durgical.com/en/biochemistry/enzymes/glucose-6-phosphate-dehydrogenase/)
- [Hemoglobin variants (HbA, HbA2, HbF, HbS, HbC)](https://durgical.com/en/biochemistry/topics/hemoglobin-variants/)

## Test yourself

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.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/biochemistry/topics/newborn-screening/)

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

Sources: [Newborn screening tests: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/007257.htm) (MedlinePlus, US National Library of Medicine, 2026); [Newborn Screening: MedlinePlus](https://medlineplus.gov/newbornscreening.html) (MedlinePlus, US National Library of Medicine, 2026); [Phenylketonuria (PKU) Screening: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/phenylketonuria-pku-screening/) (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).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/biochemistry/topics/newborn-screening/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/newborn-screening/