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Current UK NSC recommendations > Amino acid metabolism disorders

The UK NSC recommendation on Amino acid metabolism disorders screening in newborns (currently under review)


This recommendation is currently being reviewed as part of the UK NSC's regular review cycle of all policies.

The review process began in Jul 2016 and is estimated to be completed by Nov 2016.

Recommendation Systematic population screening programme not recommended
Key downloads

This is a consultation of screening for Tyrosinaemia Type 1 only.

The initial review of tyrosinaemia type 1 that was undertaken in March 2015 identified many outstanding uncertainties regarding the epidemiology, the test cut off and the long term outcomes from early treatment with Nitisinone. This evidence review has been commissioned due to the consultation responses received suggesting that studies published after the initial review’s literature search may contribute to the resolution of some of the uncertainties.


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

  • Argininosuccinate lyase deficiency
  • Citrullinaemia
  • Tyrosinaemia type I

NB: the policy for Phenylketonuria 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; Tyrosinaemia type 1, 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.
  • The review, and public consultation, suggested that screening for tyrosinaemia type 1 may be possible. The UK NSC is undertaking further work to explore the issues raised in the consultation. This includes evaluating the accuracy of the test and effectiveness of the 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
Children Living with Inherited Metabolic Diseases
Clinical Genetics Society
Faculty of Public Health
Genetic Alliance UK
Institute of Child Health
Rare Disease UK
Royal College of General Practitioners
Royal College of Midwives
Royal College of Paediatrics and Child Health
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.

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