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:
The laboratory will request an antibody investigation when a positive reaction is detected in the antibody screen. Blood group antibodies of the ABO system are universally common, but those of other blood group systems are only produced when red cells are transferred to a patient via a blood transfusion or a fetal red cell bleed during pregnancy. Theoretically, any antigen present on the transferred red cells which are not also present on the patient’s own red cells may be recognised as foreign by the recipient’s immune system and produce atypical antibodies. However, this does not routinely occur and antibody stimulation is dependent on a number of factors including the immunogenicity of the antigen involved. Rarely, these occur naturally without a stimulus and are sometimes auto-antibodies i.e. directed against the patient’s own red cells. When an atypical antibody is detected (antibody screen) it must be identified to allow for provision of compatible blood. This is especially true of antibodies that are clinically significant. These antibodies are capable of causing either transfusion reaction and/or haemolytic disease of the fetus or newborn (HDFN). Where it is not possible to identify the antibody (or antibodies) present the samples may require referral to an NHSBT reference laboratory. Blood group antibodies are only important to the patient when they require a blood transfusion or are pregnant.
Specimen container paediatric:
6mL K2 EDTA
Specimen container adult:
6mL K2 EDTA
Minimum volume paediatric:
2mL
Minimum volume adult:
6mL
Special requirements:
The antibody investigation is not available for order by the Clinical area.
Samples must be adequately filled to provide enough plasma to complete all necessary investigations.
Sample stability:
Short term storage: 24 hours at room temperature.
Once centrifuged, plasma is frozen and stored for up to 3 months.
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:
24/7
Add on test:
N/A
Interpretation:
The presence or absence of antibodies is identified by agglutination. Agglutination occurs when reagent red cells are cross-linked by the binding of either IgG or IgM patient antibodies. The pattern of reactions against a panel of reagents with known antigen status is used to identify the antibodies present. The report will indicate whether alloantibodies are present or not, what antibodies have been identified and timeframe for blood provision. The samples may require referral to an NHSBT reference laboratory depending on classification and thermal amplitude of the antibody. Once the investigation to identify clinically significant allo and/or auto antibodies is complete the laboratory can provide compatible antigen negative blood for transfusion.
Factors affecting result:
Incorrect specimen type received, clotted, haemolysed, icteric or lipaemic samples. Clotted samples may interfere with instrument pipetting and must not be used. Fibrin or particulate matter, clots, bubbles or scratches on the test cassette can interfere with reaction interpretations.