What is the significance of blood group systems in transfusion medicine for patients with a history of transfusion reactions or those requiring frequent blood transfusions?

Blood Group Systems in Transfusion Medicine

Critical Significance for Patients with Transfusion Reactions or Frequent Transfusions

For patients with a history of transfusion reactions or requiring frequent transfusions, comprehensive blood group typing beyond ABO/Rh and full red cell antibody screening are essential to prevent life-threatening hemolytic reactions and ensure compatible blood availability. 1, 2

Core Blood Group Systems and Clinical Impact

Primary Systems Requiring Testing

• ABO System remains the most clinically significant blood group system, as ABO antigens consistently produce potent, naturally occurring antibodies that can cause immediate, severe hemolytic transfusion reactions if incompatible blood is administered 3, 4

• Rh System (particularly the D antigen) is the second most clinically significant system; Rh antibodies are immune antibodies requiring prior exposure and can cause severe transfusion complications and hemolytic disease of the fetus and newborn 3, 4

• Extended phenotyping for Kell, Kidd, and Duffy systems is critical for patients requiring frequent transfusions, as alloantibodies to these antigens can result in serious hemolytic transfusion reactions 5, 4

Mandatory Pre-Transfusion Testing

• All patients require: full blood count, complete ABO/Rh typing with full red cell antibody screen, and basic metabolic panel before any transfusion 1

• For previously transfused patients: if transfused within the previous 3 months, repeat full blood count and antibody screen must be obtained within 72 hours before planned transfusion 1

• Blood samples must be collected at bedside with four core identifiers (surname, forename, date of birth, unique hospital ID) to prevent wrong-blood-in-tube events 1, 6

Management Algorithm for Patients with Transfusion History

Step 1: Enhanced Antibody Screening

• Send blood samples at the earliest opportunity for blood grouping, antibody screening, and compatibility testing 6, 1

• Patients with previous transfusion reactions require extended phenotyping to identify clinically significant antibodies beyond ABO/Rh 2, 4

• Clinically significant antibodies can cause adverse events after transfusion and must be identified before component selection 4

Step 2: Component Selection Strategy

• For patients with identified antibodies: provide antigen-negative blood components matched to avoid the specific antigens against which antibodies have formed 4, 5

• For chronically transfused patients: consider prophylactic extended matching for Rh (C, c, E, e), Kell, Kidd, and Duffy antigens to prevent alloimmunization 5, 2

• Seek expert advice from a haematologist regarding appropriate investigations, their interpretation, and optimum corrective therapy 6

Step 3: Monitoring Protocol

• Clinical observations must include heart rate, blood pressure, temperature, and respiratory rate pre-transfusion, at 15 minutes, and post-transfusion 6, 1

• If signs of transfusion reaction occur (tachycardia, rash, breathlessness, hypotension, fever): stop the transfusion immediately and contact the laboratory 6

• Management may include antihistamines, steroids, or intramuscular/intravenous adrenaline if life-threatening 6

• Measure hemoglobin before and after every unit transfused in stable patients to verify adequate response 1

Special Considerations for Frequent Transfusion Recipients

Preventing Alloimmunization

• International Society of Blood Transfusion has recognized 33 blood group systems; exposure to foreign RBC antigens through repeated transfusions increases alloimmunization risk 2, 4

• Blood group genotyping using real-time PCR can precisely identify variant antigens for clinical significance when serological methods are inadequate 5, 7

• Genotyping for RHD, RHCE, KEL, and JK alleles allows appropriate monitoring, early intervention, and improved care for chronically transfused patients 5

Documentation and Traceability

• It is a statutory requirement that the fate of all blood components must be accounted for, with records held for 30 years 6

• Patients should be informed they have received blood components before discharge, as this removes them from the donor pool 6

• The patient's general practitioner must be informed of transfusion history 6

Critical Safety Pitfalls to Avoid

• Most transfusion-related morbidity results from incorrect blood administration, not blood group incompatibility—strict adherence to identification protocols is essential even in emergencies 6

• Never proceed with transfusion if any discrepancies exist between compatibility labels and patient identification; contact the transfusion laboratory immediately 1, 6

• Hemoglobin concentration may remain falsely elevated in actively bleeding patients due to inadequate fluid resuscitation, so do not rely solely on Hb values 1

• Red cell transfusions must be completed within 4 hours of removal from controlled storage 6

Emergency Situations with Unknown Blood Type

• For patients with unknown blood group requiring emergency transfusion: use Group O RhD negative for women of childbearing potential; Group O RhD positive is acceptable for males and postmenopausal females 8, 6

• Transition to group-specific blood as soon as possible (typically within 10-15 minutes of laboratory receiving properly labeled sample) 8

• In massive bleeding, patients have minimal circulating antibodies and usually accept group-specific blood without immediate reaction, though antibodies may develop later requiring follow-up screening 8, 6