Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Pregnant women are offered a blood group and antibody screen early in pregnancy as part of routine antenatal booking (usually 10-12 weeks gestation) and again at 28 weeks gestation. This identifies women whose babies are at risk of developing Haemolytic Disease of the Fetus and Newborn (HDFN) due to developing antibodies or previously having antibodies from a previous pregnancies/transfusion.
D negative women will have a fetal RHD screen performed to determine risk of HDFN associated with anti-D.
Women with clinically significant red cell antibodies should be referred to a specialist centre and seen under the care of a consultant obstetrician. They will be monitored more closely and have regular samples referred to a reference laboratory for antibody quantitation. In the case of anti-D and anti-c (which are the antibodies most likely to cause significant HDFN) antibody quantitation is recommended every 4 weeks until 28 weeks gestation then every 2 weeks until delivery. Paternal testing may be required if a clinically significant antibody is identified during pregnancy. A group and save specimen will be requested for paternal phenotype testing to determine the % risk for the baby to have the corresponding red cell antigen. If the father is not able to be tested then fetal testing can be undertaken at the International Blood Group Reference Laboratory (IBGRL) in Bristol if considered clinically necessary. Identification of the ABO group and antibodies in pregnancy also allows the transfusion laboratory to provide suitable blood prior to labour, for delivery or any other intervention.
Specimen container adult:
6mL K2 EDTA
Minimum volume adult:
6mL
Special requirements:
Antenatal samples taken within the Trust must be ordered via EPR PowerChart and taken with the BloodTrack sample labelling system.
Community samples MUST be HANDWRITTEN by the patient’s side and accompanied with a paper transfusion request form as per the Trust Sample Labelling Policy.
The Trust operates a zero tolerance policy. Deviation from Trust Sample Labelling Policy will result in the sample being rejected and a repeat requested.
Sample stability:
Short term storage: 24 hours at room temperature. Long term storage: 7 days at 4-6°C
Transport requirements:
Sample should be transported to Laboratory Medicine Reception via GP courier, hospital air-tube system or hand delivered to maintain storage conditions. Samples must not be subjected to extreme hot or cold conditions prior to testing.
Availability:
Routine core hours Only
Add on test:
Associated investigative tests will be added on by the Laboratory as required: DAT, eluate, antibody investigation, antibody quantification/titration referral, maternal phenotype, paternal phenotype.
Interpretation:
The presence or absence of antigens and antibodies is identified by agglutination. Agglutination occurs when the red cells are cross-linked by the binding of either IgG or IgM antibody molecules.
The pattern of reactions against a panel of reagents with known antigen or antibody status is used identify the antibodies or antigens present. The report will state the patient’s blood group and indicate whether alloantibodies are present or not.
Factors affecting result:
Wrong blood in tube or laboratory transcription error.
Addressograph stickers or e-Record labels on sample tube, samples recieved >24 hours from collection, incorrect specimen type received, clotted, haemolysed, icteric or lipaemic samples, insufficient plasma provided.
Clotted samples may interfere with instrument pipetting and must not be used.
Fibrin or particulate matter, clots, bubbles or scratches on the cassette can interfere with reaction interpretations.
Unexpected/discrepant results in the blood group must be investigated further and can indicate a previous transfusion, bone marrow or stem cell transplant, weak or variant expression of the D antigen, significant sub groups of A or B, presence of an alloantibody (usually cold reacting such as Anti-M), passenger lymphocyte syndrome in solid organ transplant recipients.