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Sample types and referral information

Blood samples for molecular genetic (DNA) analysis should be 4 – 8mls (at least 1ml for new-borns), taken in an EDTA tube.

Minimum amounts of DNA:

For full gene screens (by Sanger sequencing or Next Generation Sequencing panels and which may also include MLPA analysis) – 5μg of DNA
For familial tests (of know mutations) by Sanger sequencing or genotyping tests – 1.5μg of DNA
Please contact the laboratory on 020 8725 5332 for further information on other types of sample that can be processed .

Please include at least 2 identifiers on the tube i.e. NAME and DATE OF BIRTH (which should be checked by the patient).

All samples should be sent with a Laboratory Request Form or Prenatal testing request form with the following information:

  • Clearly indicate the disease to be tested in the Molecular Genetics DNA analysis section of the form.
  • Include name (in full) of referring consultant and their hospital.
  • Include as much clinical information and family history as possible so as to be able to link family members together.

The Laboratory will assume that consent has been taken locally if the relevant section of the request form has not been completed.


  • Blood samples taken in non-EDTA tubes may not give reliable results or (in some cases) no results at all. As such, non-EDTA blood samples may not be processed.
  • Please do not send frozen blood – If there is a delay in sending the sample then it should be refrigerated overnight and sent the next day.
  • Whilst DNA can be extracted from blood in EDTA after several days, please ensure that samples reach us within a week of being taken. If there is a significant delay to a sample reaching us, it may be rejected due to poor DNA quality.

Sample rejection

Please note that samples not meeting the above criteria, or that are unlabelled or not accompanied by referral paperwork may be rejected. The referring clinician will be contacted when a sample is to be rejected in order to organise a further blood sample to be taken.

Sending samples

Blood samples should be sent by first class post, hospital transport or courier packaged according to UN3373 and Post Office guidelines. Blood samples for joint molecular genetic and cytogenetic analysis can be packaged together. DNA samples (in TE buffer) can be stably transported at room temperature. First class post is satisfactory for DNA samples, but urgent samples may be sent by courier.

The address for Specimen Reception is:

SW Thames Regional Genetics Laboratory,
Specimen Reception,
Jenner Wing, Lower Ground Floor,
St. George’s University of London,
Cranmer Terrace,
SW17 0RE

Please contact the laboratory on 020 8725 5332 if you have any queries about sample tubes or testing.

DNA banking and requesting further tests

All DNA samples (received as DNA or extracted from blood or other tissues) will be banked indefinitely unless requested otherwise.

Additional testing for other genetic conditions may be requested at any time following initial referral. This can be done in by emailing swtrgl@stgeorges.nhs.uk, in writing or by telephone, however we would ask that verbal requests are confirmed in writing.