Autoimmunity Against Red Cells
RCI investigations for autoimmunity against red cells are:
- ABO and full Rh phenotype
- The direct antiglobulin test
- Serological Investigation
- Drug associated auto-immune haemolytic anaemia
- Cold agglutinins/haemolysins and chronic haemagglutinin disease
- Biphasic haemolysins and paroxysmal cold haemoglobinuria
- Paroxysmal nocturnal haemoglobinuria
ABO and full Rh phenotype are performed on all patients. Patients who have received recent multiple transfusions may be genotyped for the same antigens by RCI.
The direct antiglobulin test is performed with broad spectrum anti-globulin reagents and class specific reagents (anti-IgG, -IgM, -IgA, -C3d,-C3c).
Investigations include the detection and identification of allo-antibodies which might be masked by auto-antibody. If free auto-antibody is present auto- or allo-absorptions or titrations are used, depending on the circumstances, to reveal clinically significant allo-antibodies. Eluates are normally prepared and tested only if the patient has been recently transfused or has received haemopoietic stem cell or bone marrow transplant.
It is recommended that patients with autoantibodies reactive at 37°C are transfused with ABO compatible units which are antigen negative for any clinically significant allo-antibody present. Units should be K negative and of an Rh phenotype compatible with that of the patient, to prevent the formation of Rh and K alloantibodies.
If haemolysis is very severe, blood compatible with an apparent specificity of the autoantibody could be transfused but clinical advice should be sought. Transfusion advice is given on a case by case basis and blood can be cross-matched by the reference laboratory if required.
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Haemolysis suspected to be associated with drug treatment can be investigated, however before sending samples, advice should be sought from scientific or consultant staff at your blood centre.
Advice should be sought from scientific or consultant staff in the NHSBT Red Cell Immunohaematology department.
A Direct Antiglogulin Test (DAT) is performed and the plasma is investigated for the presence of clinically significant red cell alloantibodies strictly at 37°C. It is not necessary to warm separate samples unless titration studies are required or specifically requested to do so by the NHSBT laboratory. Cold agglutinin titrations can be performed on request in Cold Haemagglutinin Disease patients.
SAGM-suspended cells that are ABO compatible, K negative and of a Rh phenotype matched with that of the patient are selected for transfusion. If the patient has clinically significant red cell antibodies units must also be negative for the relevant antigen(s). The blood is cross-matched by a standard antiglobulin technique strictly at 37°C. It is advised that units are transfused through a blood warmer.
Biphasic haemolysins as a cause of AIHA are extremely rare and mainly seen as a post-viral event in children. Routine investigations do not include the test for biphasic haemolysins, but where indicated, or on request the Donath-Landsteiner test can be performed if PCH is suspected. If positive the specificity of the antibody can be determined, to confirm the diagnosis.
The haemolysis in PCH is generally self-limiting. Transfusion requirements can be discussed on a case by case basis with a NHSBT consultant.
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If you require investigation of a suspected case of PNH the NHSBT laboratories will refer you to as specialist centre:
- Haematology Malignancy Diagnosis Service at Leeds Teaching Hospitals: 0113 392 6285. Hospitals may refer samples there directly for testing
- Birmingham Heartlands Hospital: 0121 424 0706
- King’s College Hospital, London, Haematology department: 0203 299 3520
Previously washed red cells were recommended for PNH patients. However, there is no evidence that the survival of washed red cells is better than that of those suspended in SAG-M.