Free Fetal DNA Screening for Fetal RhD Status
(Blood Transfusion)
Investigation : Free Fetal DNA Screening for Fetal RhD Status
Specimen type : K3E Crossmatch K3EDTA
Spec container : 6ml (PINK) 
Volume required : 1 full 6ml sample
Reference range : N/A
Turnaround : 7 working days
Special sample requirements Fully labelled and not haemolysed. Sample is referred to NHS Blood and Transplant (NHSBT) NHSBT Requirements:
  • Estimated delivery date (from dating scan) must be provided on the request form. Gestation must be at least 11+2 weeks at time of venepuncture or the sample will be rejected.
  • The sample tube must not be opened following blood collection.
  • The sample must not be used for any other testing.
  • The sample tube should be stored at room temperature.
  • The sample tube must be labelled with the following information:
  • Three unique sample identifiers including: first name and surname, date of birth, and NHS or hospitals number (please note the same number must be on both the sample tube and the request form)
  • Samples MUST be labelled, dated and signed by the person taking them.
  • Labels pre-printed prior to phlebotomy e.g. Addressograph labels are not acceptable on samples.
  • Samples must have handwritten labels.
  • Hand written alterations on either the sample or request form may make the sample invalid for testing. Any minor alterations must be initialled by the person taking the sample to be acceptable for testing.
  • Patient Preparation None
    Storage Requirements The sample tube must be stored at room temperature and transported to the laboratory.
    Clinical Application
  • It is well recognised that the identification of a pregnant patient’s blood group and antibody status plays an important role in the prevention of Haemolytic Disease of the Fetus and New Born (HDFN).
  • Patients who are RhD negative have for many years received antenatal prophylactic anti-D, to help prevent sensitisation to the D antigen from small bleeds between the fetus and maternal circulations, during the final trimester.
  • However it is also recognised that up to 40% of RhD negative patients will be carrying a fetus who is also RhD negative. This makes the administration of prophylactic anti-D unnecessary, so making the risk associated with the administration of a blood product, greater than the advantages experienced by receiving the product.
  • In 2015, NHSBT began to routinely offer an automated service which allows all RhD negative patients to be tested, to determine the RhD status of the fetus, and permit a more individualised treatment. Samples will be sent to NHSBT for the status to be determined.
  • Clinical Interpretation The three possible results will be:
  • The fetus is RhD positive – anti-D required
  • The fetus is RhD negative – anti-D not required
  • The fetus is indeterminate – treat as RhD positive – anti-D required
  • EQA Scheme As per NHSBT
    CPA/UKAS Accredited All NHSBT RCI laboratories are accredited to ISO 15189 by United Kingdom Accreditation Service (UKAS) for the clinical services they provide. They are also licensed by the Medicines and Healthcare products Regulatory Agency (MHRA) for the services that fall under the Blood Safety and Quality Regulations (BSQR).


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