DNA can be extracted from solid tissue samples for molecular genetic testing in situations where blood cannot be obtained, e.g. aborted tissue, stillbirths or other post mortem study. DNA is extracted and stored from all suitable solid tissue samples.
Fibroblast cultures can be used to supplement blood cultures in patients who may have mixed cell types (mosaics). Cultured cells can also be sent to other laboratories for the diagnosis of some inherited metabolic disorders.
Samples of solid tissues such as skin, cord, foetal tissue or products of conception (“POCs”) may be sent to the laboratory for genetic studies. These may include the following:
- Stillbirths or miscarriages with any dysmorphic features/physical abnormalities
- Stillbirths or miscarriages where parents are known to carry chromosome rearrangements or abnormalities
- Early spontaneous abortions with a history of 3 recurrent miscarriages
- Confirmation of karyotypes detected at prenatal diagnosis
- Termination of pregnancy for multiple abnormalities
- Suspected biochemical defect (tissue will be cultured for metabolic studies and fibroblasts stored by prior arrangement)
Please note: the following specimens should not be sent for genetic studies
- Large complete ERPC samples/complete products of conception
- Primary anoxia
- Birth injuries
- Placental difficulties
- Infections/toxaemia of mother and/or foetus
- Cervical/hormonal incompetence
- Macerated skin samples (please send placental sample instead)
- First or second miscarriage/still birth if no dysmorphic features/physical abnormalities
Investigation of mosaicism can also be undertaken by FISH (Fluorescence In Situ Hybridisation) on buccal cell samples.
- Sterile tissue culture transport medium is available from the Laboratory and can be requested by e-mailing email@example.com .The transport medium should be stored frozen and must be defrosted completely before use. The expiry date is recorded on the bottle. Do not use CVS transport medium for tissue samples as it contains different supplements.
- Samples must not be sent in formal saline or other preservative. If transport media is unavailable sterile normal saline may be used.
- Samples should be sent as soon as possible to the laboratory (first class post is acceptable). Delay in receipt is a major factor in rate of infection and the failure of cell growth in tissue samples.
- Samples should be stored in a fridge if there will be a delay in transport (do not freeze any specimens).
- Specimens should be placed in a sterile plastic universal type bottle in transport medium.
Skin biopsy from aborted foetuses/stillbirths:
- The biopsy is usually taken from the upper fleshy part of the thigh or upper arm.
- Rinse the limbs thoroughly with sterile normal saline.
- The biopsy should be 1-2cm in length to the depth of the underlying muscle and placed into transport media. Outermost layers are often in poor condition and may not yield growth.
- Where possible, a sample of fresh placental tissue or cord may be sent in addition to foetal tissue, as this can improve the likelihood of producing a result.
Skin biopsy from a live patient:
- The biopsy is usually taken from the inside of forearms or (in babies) the iliac crest. A local anaesthetic should be avoided where possible as this can impair cell culture.
- The biopsy should be 2-3mm wide and deep enough to include the whole thickness of the epidermis and adjacent connective tissue, in transport media.
- Other samples e.g. post mortem specimens, ovarian or testicular biopsies, etc., should be sent as above.
Anticipated reporting time: Within 28 days
Methods of Analysis
For post mortem samples the analysis will be by molecular genetic methods
The testing will consist of two parts:
QF-PCR to detect common trisomies (13, 18 and 21), triploidy and sex chromosome aneuploidy; this test will also identify complete molar pregnancies. More information is available in the Prenatal Diagnosis section.
If no abnormality is detected by QF-PCR that explains foetal loss, further testing by microarray Comparative Genomic Hybridisation (aCGH) looking at copy number change across the whole genome, will be undertaken. This will identify all trisomies and unbalanced rearrangements where there is gain or loss of a region. This technique does not detect balanced translocations or rearrangements that do not alter the copy number of the probe target sequences. It does not reliably detect mosaicism
- For the majority of abnormal results found (excluding full trisomy of non-acrocentric chromosomes), parental blood samples will be requested to allow us to exclude the presence of a parental structural rearrangement and ascertain future reproductive risk.
- Whilst skin samples (0.5mm2/20mg) are preferred for DNA extraction, if this is not available placenta or other foetal tissue can be used.
- DNA will be stored indefinitely on all samples processed; therefore parents should be made aware of this and their consent given.
Any tissue material remaining after the sample has been forwarded for molecular tests will be disposed of in accordance with the Laboratory Disposal and Sensitive Disposal Policy once the molecular tests have been completed and fully reported. Samples from pregnancy losses are collected and transported separately from clinical waste and are incinerated. This includes foetal skin samples and samples which contain placental and foetal tissue. A record is retained for the disposal of these samples.
Placental biopsies are disposed of with the routine clinical waste.
We are not able to offer any alternative methods of disposal
For live patients
- Where a mosaic chromosome abnormality is suspected cells will be cultured and testing will be carried out by chromosome analysis.
- Live patients where biochemical testing is required will have cells cultured and held in long term storage.
Additional Solid Tissue Tests:
QF-PCR for foetal sexing: If requested, uncultured foetal tissue may be used for immediate foetal sexing by QF-PCR.
Formalin Fixed Paraffin Embedded (FFPE) Tissue Samples from Foetal Post Mortem:
Paraffin Embedded Tissue Samples can be used for interphase fluorescent in-situ hybridisation (FISH) analysis for the determination of trisomy 13, 18, 21 and sex chromosomes if fresh material is not available. We are currently validating DNA extraction from FFPE tissue for QF PCR testing.
Samples should be
- 10 sections mounted on positively charged or coated slides
- 4 micrometres thick
- Baked over night
- Not more than 3 days old
- Please contact the laboratory for further advice and details.
Please also send Shaves/Curls: 8 10μm thick freshly cut curls for laboratory validation of DNA extraction and QF PCR testing.
Cells for Diagnosis of Other Genetic Disorders:
Cells can be cultured for analysis of metabolic and molecular genetic disorders at the request of a referring consultant. A referral letter is required with clinical information to be sent with the sample to the laboratory carrying out the test. The Bristol Genetics Laboratory (BGL) has close liaison with a large number of biochemical genetics and molecular genetics laboratories and is pleased to make any of the necessary arrangements for sending samples to the test laboratory for analysis. Samples can be processed to include the extraction of DNA and the culturing of cells for analysis by other laboratories. As far as practicable samples are only sent to CPA accredited laboratories.
The department has facilities for long-term storage of fibroblast cells in -152°C freezers. This enables further testing to be undertaken. Cells are stored from all live patients where tissue culture is successful and from pregnancy loss samples where this is requested by the referring consultant and with patient or parental consent (respectively).
Our current storage policy states that we will culture and store viable cells on samples from the following post mortem referrals;
• sudden unexpected death in infancy
• specific clinician request
We will not store any of the above where a chromosome abnormality is detected.
This policy is subject to review. Long term cell storage will incur additional costs.
Further advice is available from the Clinical Genetics Service.
Buccal Cell Samples for the Investigation of Mosaicism:
Buccal cells can be used to evaluate suspected mosaicism in live patients and may be a suitable and less invasive alternative to skin biopsies. Cell preparations of this type are only suitable for in situ hybridisation studies where a specific abnormality is suspected.
The most frequent use of this type of sample is for the investigation of aneuploidy (full, partial or mosaic) e.g. Pallister Killian syndrome, mosaic Down syndrome, or parents of recurrent aneuploid conceptions.
Limitations: This test is not appropriate for the investigation of non–specified mosaicism, or for situations where full karyotyping is indicated. Buccal cell preparations are not appropriate for multi telomere studies.
Buccal brushes (small) are used to obtain buccal cell preparations. They may be placed in a small container of sterile saline.
Samples are usually taken in consultation with the Clinical Genetics Service. Buccal cell kits are available upon request from the laboratory.
Samples should be sent to the Bristol Genetics Laboratory (BGL) by first class post
Last updated: 30/07/2019