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Example clinical scenario

A family attend the paediatric clinic concerned because their three-year-old son’s development is delayed. He sat at one year, was walking at two and a half years and, at the age of three has a few single words but is not talking in sentences. He has some dysmorphic features and was diagnosed with an atrial septal defect following the detection of a heart murmur at the newborn check.

When to consider genomic testing

Genomic testing should be considered if a patient presents with:

  • moderate to profound intellectual disability;
  • intellectual disability (of any severity) associated with:
    • behavioural problems, including autism spectrum disorder;
    • other medical problems, such as seizures;
    • congenital anomalies, such as congenital heart disease;
    • atypical growth patterns (such as growth restriction, overgrowth or asymmetric growth);
    • microcephaly or macrocephaly;
    • dysmorphic features;
    • developmental regression;
    • atypical MRI brain findings; and/or
    • a family history of learning disability (particularly if X-linked pattern) or of multiple miscarriages.

What do you need to do?

  • Consult the National Genomic Test Directory. From here you can access the rare and inherited disease eligibility criteria, which provides information about individual tests and their associated eligibility criteria. You can also access a spreadsheet containing details of all available tests.
  • To find out which genes are included on different gene panels, see the NHS Genomic Medicine Service (GMS) Signed Off Panels Resource.
  • Decide which of the panels best suits the needs of your patient or family. For developmental conditions there are a number of available panels, including:
    • R377 Intellectual disability (microarray only): This should be considered if you only want to investigate chromosomal causes, which will require a microarray;
    • R29 Intellectual disability: This should be considered if you want to investigate chromosomal and single-gene causes of developmental delay or intellectual disability (the test is a whole genome sequencing (WGS) panel of all genes known to cause intellectual disability); and
    • R27 Paediatric disorders: This should be considered if there is developmental delay or intellectual disability in association with congenital malformation or overgrowth, and you would like to investigate chromosomal and single-gene causes. The test is a WGS ‘super panel’ (a panel comprised of several different constituent panels forming one large panel). Requesting R27 currently requires authorisation from clinical genetics services.
  • Certain conditions, such as imprinting disorders or nucleotide repeat expansion disorders, are not reliably picked up by sequencing tests and require additional specialist tests. However, WGS pipelines are currently being optimised to more reliably detect fragile X syndrome. If you have a strong clinical suspicion of one of the following conditions, you may wish to undertake more targeted tests (also listed) before considering broader testing.
  • For tests that are undertaken using WGS, including R29 and R27, you will need to:
  • For tests that do not include WGS, including R377, R47, R48 and R53:
    • you can use your local Genomic Laboratory Hub test order and consent (RoD) forms; and
    • parental samples may be needed for interpretation of the child’s result. Parental samples can be taken alongside that of the child, and their DNA stored, or can be requested at a later date if needed.
  • The majority of tests are DNA based, and an EDTA sample (typically a purple-topped tube) is required. Exceptions include karyotype testing and DNA repair defect testing (for chromosome breakage), which require lithium heparin (typically a green-topped tube).
  • Information about patient eligibility and test indications was correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

Resources

For patients

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  • Last reviewed: 05/03/2024
  • Next review due: 05/03/2025
  • Authors: Professor Kate Tatton-Brown
  • Reviewers: Dr Elaine Clark, Dr Amy Frost, Dr Eleanor Hay