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

Chromosomal microarray and karyotype

Cytogenetic testing including microarray and karyotype will be performed as appropriate depending on the clinical indication. For further information about the testing available and the clinical eligibility for these tests please refer to the National Test Directory.

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 microarray 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.

Limitations

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 12/05/2025. Please note that if printed, the information is only valid on the day of printing.