Atypical antibodies and blood grouping

The Red Cell Immunohaematology laboratories provide a comprehensive reference service for the investigation of grouping and antibody problems. This service is supported by the International Blood Group Reference Laboratory (IBGRL).

Atypical red cell antibodies: serological and crossmatching problems

Samples referred for the investigation of atypical antibodies will be tested both to confirm the specificity of the antibodies and to exclude the presence of additional alloantibodies. RCI reference laboratories have access to a large number of phenotyped red cells in addition to routine antibody identification panels to enable a full investigation to be completed. The patient’s Rh and K phenotype will be performed on the first sample received from that patient, plus testing for any other implicated antigens. Clinical advice on further transfusion support is given as appropriate. Results are entered on the NHSBT national patient database and an antibody card will be issued for patients with irregular antibodies.

Patients who may require long term transfusion support are phenotyped for all the major blood group antigens. Patients who have received recent multiple transfusions may be genotyped for the same antigens by RCI.

Provision of cross-matched units in difficult cases

Where the provision of crossmatched units is problematic, the RCI laboratory can undertake the crossmatch. Please make the request for crossmatched units clear on the request form and / or discuss with your laboratory.

Red cell genotyping

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.

a, Jk^b, Fy^a, Fy^b, Do^a, Do^b

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.

Haemolytic transfusion reactions

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 grouping and antibody screening

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.

Positive direct antiglobulin test

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.

Transfusion of RhD positive blood to RhD negative recipients

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.

Investigation of IgA deficiency and IgA antibodies

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.