Learn which sample types a laboratory may accept for clinical exome sequencing, and when family samples or special precautions are needed.
What is the purpose of sample collection?
A WES laboratory needs DNA of suitable quantity and quality. Extraction and preservation methods depend on the sample. Peripheral blood is common, while some validated workflows also accept saliva or buccal swabs.
The laboratory’s approved protocol determines which samples are acceptable. Do not choose a tube, storage method or shipping condition based only on general online advice.
Peripheral blood: a common choice
Many clinical services request a specific volume of venous blood in an appropriate collection tube. The exact volume, anticoagulant, permitted transport time, temperature and accompanying paperwork are set by the laboratory.
Requirements may differ for infants, children and adults. Blood collection for exome sequencing is used to obtain DNA from cells; it is not the same as checking current blood counts or blood chemistry.
When are saliva or buccal swabs used?
Some laboratories use saliva or cheek-cell samples for genetic analysis. Collection can be convenient, but DNA quantity, contamination and collection technique can affect sequencing quality.
Follow the instructions supplied with the approved kit. Use a non-blood sample for clinical WES only when the performing laboratory has explicitly confirmed that it is suitable.
When might a special sample be needed?
After bone-marrow or stem-cell transplantation, blood DNA may substantially reflect donor cells rather than the recipient’s original inherited genetic makeup. In suspected tissue-specific mosaicism, blood may also fail to capture the relevant variant.
The clinician and laboratory should agree on an appropriate tissue and method. Disclose a history of transplantation, recent transfusion and relevant blood disorders before sampling.
When are samples from family members required?
In trio exome sequencing, samples are generally collected from the person being investigated and both biological parents. A duo or broader family study uses samples from the relatives specified by the clinical team.
Identity, family relationships and informed consent are managed under the laboratory’s protocol. Family testing is not required for every patient.
Checklist before the appointment
Prepare the referral, identification, relevant medical records, earlier genetic test results and family history. Ask which sample is required, which container to use, how to transport it, how long it remains usable and what consent forms are needed.
Also ask whether any specific preparation is necessary. A few minutes of coordination can prevent repeat sampling and avoidable delays.
Frequently asked questions
Do I need to fast before WES?
Fasting is usually not necessary for standard DNA extraction from blood, but follow the laboratory’s instructions and those for any simultaneous tests.
Can samples be shipped from another city?
Some laboratories accept shipped samples. Confirm packaging, shipping temperatures and maximum transit time in advance.
Scientific resources for further reading
For case-specific advice and current laboratory requirements, consult our services or genetic counseling team.
