Current UK NSC recommendations > Amino acid metabolism disorders

The UK NSC recommendation on Amino acid metabolism disorders screening in newborns

Recommendation Systematic population screening programme not recommended
Last review completed March 2015
Next review due in 2018/19
Key downloads

This policy covers the following rare inherited amino acid metabolism disorders:

  • Argininosuccinate lyase deficiency
  • Citrullinaemia

NB: the policy for TyrosinaemiaPhenylketonuria and Homocystinuria screening are considered separately.


Find general information about population health screening.

Why is screening not recommended by UK NSC?

The UK NSC does not currently recommend screening for the amino acid metabolism disorders; Citrullinaemia (CIT) and Argininosuccinate lyase (ASL) deficiency in newborn babies. This is because:

  • Babies with CIT often develop symptoms before the results of the screening test would be available. Additionally, the test would falsely identify some healthy babies as having the condition.
  • The long term effects of ASL Deficiency, such as liver disease and brain damage, appear to be unaltered by early treatment


More about Amino acid metabolism disorders

Amino acid metabolism disorders are a group of inherited conditions caused by a particular enzyme (a chemical found naturally in the body) being faulty or missing. This leads to problems breaking down certain amino acids. Amino acids are the building blocks of proteins and are metabolised in order to provide energy or to make other needed compounds.

This disorder leads to a build up of unwanted chemicals that can cause damage to vital parts of the body such as the liver.

» Read more about amino acid metabolism disorders at the Climb National Information Centre for Metabolic Diseases website


British Association of Perinatal Medicine
British Inherited Metabolic Disease Group
Clinical Genetics Society
Faculty of Public Health
Genetic Alliance UK
Institute of Child Health
Metabolic Support UK
Royal College of General Practitioners
Royal College of Midwives
Royal College of Paediatrics and Child Health
Royal College of Physicians
Royal College of Physicians and Surgeons of Glasgow
Royal College of Physicians of Edinburgh
Save Babies Through Screening Foundation UK
UK Newborn Screening Laboratories Network

The stakeholder groups will be involved when the recommendation is next reviewed. If you think your organisation should be added, please contact us. More information for stakeholders can be found in appendix C of the UK NSC evidence review process.

Related documents

icon Amino acid metabolism disorders: One page recommendation summary (2015) (PDF document, 70KB, 08/06/15)
icon Amino acid metabolism disorders: UK NSC summary 2015 (PDF document, 939KB, 08/06/15)
icon Ethical, Social and Legal Issues with Expanding the Newborn Blood Spot Programme (PDF document, 2.13MB, 21/11/14)
icon Review of screening for Citrullinaemia & ASLD - 2014 (PDF document, 955KB, 26/07/17)
icon Tyrosinaemia: UK NSC recommendation summary (June 2017) (PDF document, 327KB, 04/08/17)

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