Chromosome Analysis

Introduction

Cells from a variety of samples (chorionic villus, amniotic fluid, blood and solid tissue) are cultured. Chromosomes are visualised using the G-banding technique. Normal males and females carry 46 chromosomes; two of these are the sex chromosomes. Chromosome analysis can be used to detect numerical abnormalities where there is complete loss (e.g. Turner syndrome, 45,X) or gain (e.g. trisomy 21 or Down syndrome, 47,XY,+21) of a chromosome. It can also detect structural chromosome changes where there is partial loss or gain of chromosome material. Chromosome analysis can also detect balanced structural anomalies such as reciprocal/Robertsonian translocations and inversions. We accept referrals encompassing a whole spectrum of referral reasons.

Referral information

Postnatal Referrals

We accept blood samples from babies with ambiguous genitalia, suspected aneuploidies (trisomy 21, trisomy 13 or trisomy 18), for confirmation of a chromosome abnormality detected prenatally or for suspected sex chromosome aneuploidy. We also accept referrals from couples who are undergoing tests for infertility (IVF couples, azoospermic males) and patients with problems of sexual development (suspected Turner syndrome, suspected Klinefelter syndrome, delayed/premature puberty, or premature ovarian failure). We accept referrals for follow-up studies following detection of a chromosome abnormality either in another family member or following a pregnancy loss. We also accept referrals for patients with a family history of a balanced rearrangement (inversion, insertion or translocation). Samples from babies under the age of three months and from pregnant couples are classed as urgent samples (see reporting times).

Prenatal Referrals

We accept chorionic villus and amniotic fluid samples referred for increased nuchal translucency/thickness, increased serum screening risk, increased maternal age, abnormalities seen on ultrasound scan and a family history of balanced rearrangement. Samples will be tested by QF-PCR initially  and will only proceeded to chromosome analysis if an aneuploidy is detected by QF-PCR  We also accept samples referred for a family history of biochemical or molecular disorder; however these are only cultured by the cytogenetics department and the sample/cultured cells forwarded on to the relevant laboratory for specific testing. All prenatal samples are classed as urgent samples.

Solid Tissue Referrals

We accept skin punch biopsy samples from patients referred with suspected mosaicism (e.g. Hypomelanosis of Ito or Pallister-Killian syndrome). We also accept tissue samples from pregnancy loss but these samples are processed by QF-PCR and, where appropriate, by array CGH.  It is essential that the date of delivery is included on all samples from pregnancy loss.

Technical information

All samples referred for chromosome analysis will be cultured and will undergo G-banded chromosome analysis. Samples from patients for array CGH or chromosome breakage analysis do not undergo chromosome analysis. Additional tests such as rapid aneuploidy screening using QF-PCR may also be requested and these requests must be specifically recorded on the referral card. Additional tests may be instigated by the laboratory if the chromosome analysis findings require further investigation.

Price & reporting times

NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases please contact the lab for prices. The requirements for postnatal samples are a blood sample in Lithium heparin.

Test Price (£ ex VAT) TRT *
Prenatal chorionic villus sample POA 10 cd
Prenatal amniotic fluid sample POA 14 cd
Urgent postnatal blood sample POA 10 cd
Routine postnatal blood sample POA 28 cd
Solid tissue sample POA 28 cd
QF-PCR

Test validation & quality assurance - information for users

In some postnatal cases the quality of the chromosome preparations may be sufficient for the exclusion of numerical chromosome abnormalities and large structural chromosome rearrangements only. In these cases we offer to repeat the blood test to rule out other smaller structural chromosome abnormalities. Standard chromosome analysis cannot detect chromosome deletions/duplications smaller than 5Mb in size. Chromosome analysis therefore cannot rule out a diagnosis of syndromes or conditions associated with smaller chromosome deletions or DNA mutations. In these cases microarray or molecular genetic testing will used instead of chromosome analysis.

Sample requirements

5ml Lithium Heparin blood sample (1-2ml volume sufficient for younger/difficult to bleed patients)

Referral guidelines

Please see our referral guidelines for more information.

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