Blood Culture and Karyotyping
Referral Categories:
The main referral categories include:
- Abnormal newborns
- Investigation of infertility
- Parents of children with a known chromosome abnormality
- Family follow-up studies
- Screening of patients and donors for IVF
Referral for:
Prader Willi and Angelman’s Syndrome
In addition to routine cytogenetic analysis, all Prader-Willi and Angelman syndrome cases are passed on for molecular genetic testing to determine if there is an abnormal DNA pattern present and to check for uniparental disomy.
Chromosome Breakage Syndrome
Testing of patients at risk of Fanconi anaemia, ataxia telangiectasia or Blooms syndrome is undertaken by the Sheffield Diagnostic Genetics Service. Please see their website https://www.sheffieldchildrens.nhs.uk/sdgs/constitutional-genetics/ for further information.
Samples can be forwarded to the Yorkshire and North East Genomic Laboratory Hub, Central Lab to be dispatched to Sheffield, however, this could delay testing and reduce test success rates.
Microdeletion testing
Patients with a suspected deletion of 22q11.2 (DiGeorge syndrome, Velo-cardio-facial syndrome, Schprintzen syndrome, etc) are karyotyped and tested with a commercially acquired FISH probe specific to 22q11.2. If these tests give normal results, SNP array is offered. This strategy is occasionally employed for other suspected micro-deletion syndromes such as William’s syndrome, however, this is dependent on the most appropriate testing strategy determined by the lab.
For other suspected micro-deletion referrals, SNP array testing will be used.
SNP array
This is a technique for detecting abnormalities of genomic copy number. It is a high resolution whole genome screen which detects genetic imbalances at 50kb resolution. From the 1st January 2019 SNP array has replaced Array Comparative Genomic Hybridization (array CGH) as a first line test for paediatric patients presenting with unexplained learning difficulties / developmental delay / behavioural problems (including autism and referrals for the fragile X phenotype) and patients with dysmorphism / multiple congenital abnormalities suggestive of a chromosome abnormality.
Further clinical advice is available from the Department of Clinical Genetics, Chapel Allerton Hospital, Leeds.
Test Requirements:
Chromosome analysis
Requirements: 1-2 mls (minimum) peripheral blood in a lithium heparin tube (green or orange top) & referral card completed with:
- Name
- NHS number
- Date of birth
- Address
- Comprehensive clinical details.
Rapid Aneuploidy Screening
A rapid result (within 24 hours for samples received Monday - Friday) is available for samples referred with a suspected aneuploidy involving chromosomes 13, 18 or 21. It is obtained using QF-PCR or FISH probes which allow us to rapidly assess the number of chromosomes 13, 18, and 21 present.
QF-PCR or FISH testing is usually undertaken on samples received in lithium heparin.
Sample Tubes
Blood samples for chromosome analysis should be collected in a lithium heparin tube (orange or green top), and mixed well to prevent clotting. It is important to ensure that the sample tube contains lithium heparin irrespective of the colour of the tube top.
Blood samples for SNP array should be collected in EDTA.
Preferred volumes of blood
- Adults 5ml
- Children 2-5ml
- Infants 1-2ml
More blood may be needed if chromosome breakage studies are required.
Sample Transport
Please see laboratory contact page for address details.
Cytogenetic analysis requires living cells. Please ensure that the sample reaches us as quickly as possible (within 48 hours). First class post is satisfactory for non-urgent samples.
Urgent samples should be sent by courier or taxi.
Samples should not be frozen, exposed to excess heat or stored in formalin.
If there is a delay in transit please store the sample at 4°C (in a refrigerator).
Please try to avoid sending samples at weekends or bank holidays as post is not delivered on these days.
When sending samples by post a secure container should be used to conform to current postal regulations, i.e. P650 and UN3373 applicable. For more information please see here.
Urgent Samples
Cases treated as urgent are all new borns, cordocentesis specimens, pregnant couples including follow up of prenatal diagnosis, children awaiting surgery and others cases as discussed with the laboratory.
Reporting of Results
Urgent cases - Usually within 10 days which is within the national guidelines. An aneuploidy screen can often be done overnight as a QF-PCR or Fluorescent in situ Hybridisation (FISH) test (please contact the laboratory).
Other cases - We attempt to report within the national guidelines which are within 42 calender days. If results are required earlier please contact the lab.
Complex abnormalities, or abnormalities that are difficult to interpret, may require FISH or SNP array to resolve the karyotype, this may delay some results.
Results are sent to the referring clinician. Complex abnormal results are usually telephoned prior to the written report being sent and the interpretation and implication discussed. Abnormal results from urgent cases will be telephoned to the referring clinician.
In response to telephone enquiries, only normal results or those which confirm a previous finding are given to a clinician’s secretary or the clinic sister. All other results are only given to clinicians.
