Atypical antibodies and blood grouping

Red cell blood group determination is undertaken in RCI laboratories to support and enhance timely decision-making to improve the safety of transfusion and improve patient outcomes.

In particular, the ability to determine blood type in previously transfused patients, and those with immunoglobulin coated cells will be of significant benefit. The service is available for referrals from all users but is provided from Tooting, Colindale, Birmingham, Barnsley, Filton, and Newcastle sites.

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The use of this test will be determined by RCI and clinical staff as part of the investigation. There is no facility to request this test from RCI, and there is no charge applied when it is undertaken.

Blood grouping results will be reported as phenotype or genotype depending on the method employed.

ABO typing, Rh phenotyping, DAT and antibody screen / identification will be performed on both pre- and post-transfusion samples if available.  If no antibodies are detected by standard methods a more sensitive method may be applied.  Eluates will be prepared as necessary and tested against a panel of cells, including A₁ and B cells, by an IAT method.  An ABO, Rh phenotype and DAT will be performed on any implicated red cell units and re-crossmatching will be carried out against the pre- and post-transfusion samples. 

If possible please include a clotted sample to allow testing of serum The tests above will be performed using plasma if this is the only patient sample(s) available.  However, if all tests for antibodies are negative and there is strong evidence of haemolysis, a serum sample may be requested in order to repeat the tests.  It is possible that some weak, complement-dependent antibodies will be more readily detected in serum.

If all reactions are negative, further investigations will be considered for non-haemolytic transfusion reactions e.g. HLA antibodies, anti-IgA. RCI is a UKAS accredited medical laboratory No.8740. RCI’s accredited services are listed at www.UKAS.com. IgA deficiency and anti-IgA testing by flow cytometry method is currently not UKAS accredited.

Transfusion advice

if further blood is required urgently the NHSBT will provide ABO, Rh phenotype matched, K negative units. Pre-transfusion tests will be performed using  the post- transfusion sample.

Routine ABO/RhD groups can be performed with or without an antibody screen and a blood group card can be issued.

Problems with ABO / RhD grouping

Samples can be referred for investigation if anomalous results are obtained with routine ABO or RhD grouping, for example, to distinguish between "D variants" and weak D antigens. In case of ABO grouping problems saliva may be requested. It is important to include relevant clinical data. A blood group card can be issued.

In a high proportion of DAT positive cases with free autoantibodies referred to the RCI laboratories, alloantibodies are also present.  Therefore it is recommended that samples from patients requiring a transfusion and with a positive DAT are referred so that clinically significant alloantibodies, which might be masked, can be detected and identified.  In these cases absorptions may be performed and adequate volumes of samples are required.

In recently transfused patients who develop a positive DAT, this may be caused by alloantibodies bound to donor red cells (indicating a possible delayed haemolytic reaction); in such cases an eluate needs to be prepared for which at least 3mL of packed red cells are needed.

In patients with a positive DAT and a negative antibody screen who need transfusions, samples should not routinely be referred prior to each transfusion episode.  An eluate is indicated only if there is evidence of a delayed haemolytic transfusion reaction, a change in serology or if a higher frequency of transfusion than normal is required to maintain an adequate level of haemoglobin.  The DAT may be positive in patients or in healthy individuals without overt haemolysis.

If you require blood cross-matched for a patient with a positive DAT and free auto-antibody please speak to a member of the RCI laboratory staff.

If RhD positive blood has been given to a RhD negative female recipient of child bearing potential, the case should be discussed with a NHSBT medical consultant. The volume of RhD positive red cells infused can be calculated and advice given on the management of the patient. The removal of these cells from the patient´s circulation can be monitored by flow cytometry.

In cases of anaphylactic transfusion reactions, or other indications, samples can be referred to test for IgA deficiency and the presence of antibodies to IgA. RCI is a UKAS accredited medical laboratory No.8740. RCI’s accredited services are listed at www.UKAS.com. IgA deficiency and anti-IgA testing by flow cytometry method is currently not UKAS accredited.

Transfusion advice

Advice should be sought from the scientific or consultant staff in the Red Cell Immunohaematology department.