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Paediatric tests

Sample requirements

Samples should ideally be sent to the Cytogenetics Department on the same day/next day. Where a delay is inevitable, such as over weekends, please store the sample in a refrigerator before sending on the next working day but please DO NOT FREEZE. Lithium heparin and EDTA tubes are suitable for cytogenetic testing depending on the test required, please see below, samples in other tubes will be rejected. For sample labelling, sample tube guide and completion of referral form criteria please see referral requirements.


Karyotype and FISH

Please send a 1-2ml blood sample, well mixed, in a lithium heparin (usually green cap) container. Gel tubes may be used but please do not centrifuge or allow to separate. For neonates or children who are difficult to bleed we will attempt to process smaller blood samples.


Chromosomal Microarray

For microarray please send a 3-5ml blood sample in an EDTA container. Only one EDTA tube is required. Bloods in other tubes will not be processed.


Fanconi Anaemia

Fanconi Anaemia referrals should be sent to Sheffield Diagnostic services. Please see SDGS website for details.


Acceptance and rejection criteria

Lithium heparin is the preferred tube for karyotype testing. Bloods received in EDTA will be processed but the quality may be compromised. Bloods in any other tube will not be processed. For paediatrics the volume required is 1-2ml, smaller volumes may be attempted but the success or quality of the test may compromised.

For urgent referrals or unrepeatable samples, if blood samples are received clotted or haemolysed, processing is usually attempted, however this may compromise the success or quality of the test. For a routine referral, the sample may be rejected and a repeat sample requested.


Referral categories and tests

Karyotype - neonates

  • Features suggestive of Down (trisomy 21), Patau (trisomy 13) or Edwards (trisomy 18) syndromes
  • Ambiguous genitalia or gender uncertainty
  • Dysmorphic features, hypotonia or other congenital abnormalities
  • Confirmation of a prenatal cytogenetic test


Karyotype - paediatrics

  • Features suggestive of Turner syndrome (e.g. short stature, delayed secondary sexual development) 
  • Other disorders of sex development

Targeted G-banding

Targeted G- banding will be performed if a known chromosomal rearrangement is investigated e.g. A known familial rearrangement; aneuploidy detected by FISH/QF-PCR/microarray testing; a particular pattern of CNVs detected by microarrayarray testing suggestive of a balanced parental rearrangement.

FISH - Fluorescence In Situ Hybridisation

We have FISH probes available for some microdeletion syndromes. For specific exclusion of these syndromes please indicate on the referral card which syndrome is to be tested for. For other FISH tests please contact the Cytogenetics Department to discuss your requirements. Please note, that microarray analysis for probands suspected to have a microdeletion syndrome is a more appropriate test. Please see neurodevelopmental disorders.


Chromosomal microarray - paediatrics 

For neurodevelopmental disorders, we recommend patients meet some of the following criteria:

  • Developmental delay
  • Learning disability
  • Facial dysmorphism or congenital abnormalities
  • Behavioural problems/autistic spectrum

Please refer to the link for neurodevelopmental disorders. Please see The National Genomic Test Directory for other referral categories relevant for microarray testing. 


Reporting times

Please see our Target Reporting Times.



Please see our limitations of testing page.


Storage and future testing

Fixed material from neonate and paediatric samples is archived for at least 6 months from the date of receipt. Cases with a normal karyotype are then discarded; cases with a structural chromosome abnormality are stored for 5 years. For samples referred for microarray testing, the remaining DNA is stored for at least 30 years within Molecular Genetics. Subsequent genetic testing can be requested at any time within these periods but may not be possible depending on the quality of the material available.

Page last updated 28/02/2023. Please note that if printed, the information is only valid on the day of printing.

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