What are the ABO/D type and additional criteria for selecting a donor unit for a possible exchange transfusion in a newborn with a positive Direct Antiglobulin Test (DAT) and hemolytic disease of the newborn (HDN)?

Selection Criteria for Exchange Transfusion in a Newborn with Positive DAT

For a newborn with O negative blood type and positive DAT due to maternal antibodies, the blood for exchange transfusion should be O negative and must meet additional criteria including compatibility with maternal antibodies, irradiation, leukoreduction, CMV-negative status, fresh units (<7 days old), and appropriate crossmatching.

Blood Type and Compatibility Requirements

The newborn in this case has:

• O negative blood type
• Positive Direct Antiglobulin Test (DAT)
• Mother is A positive with positive antibody screen
• Second child required phototherapy for jaundice
• Elution panel shows the same specificity as panel 1A

Primary Selection Criteria:

1. ABO/D Type: O negative RBCs must be used to match the infant's blood type 1

2. Compatibility with Maternal Antibodies: The donor unit must be negative for the antigen against which the maternal antibody is directed (as determined by the elution panel) 1, 2

3. Crossmatch Requirements: Blood must be crossmatched against the mother's serum (not the infant's) to ensure compatibility with maternal antibodies 1

4. Irradiation: All blood products for exchange transfusion in neonates should be irradiated to prevent transfusion-associated graft-versus-host disease 1

5. Leukoreduction: Blood should be leukocyte-reduced to minimize risk of cytokine release and febrile reactions 1

6. CMV Status: Blood should be CMV-negative or leukoreduced to prevent CMV transmission 1

Additional Critical Requirements

1. Fresh Blood: Units should be less than 7 days old to ensure adequate red cell function and minimize potassium load 1

2. Processing: Modified whole blood (red cells and plasma) should be used rather than packed red cells alone 1

3. Screening: Blood should be screened for infectious diseases according to standard blood bank protocols 1

4. Warming: Blood must be properly warmed to body temperature before transfusion 1

Clinical Management Considerations

This case represents hemolytic disease of the newborn (HDN), likely due to maternal antibodies directed against the infant's red blood cells. The positive DAT confirms antibodies are bound to the infant's RBCs 3, 4.

Indications for Exchange Transfusion:

• Total serum bilirubin (TSB) reaching exchange transfusion threshold based on gestational age and risk factors 1
• TSB ≥25 mg/dL (428 μmol/L) at any time is considered a medical emergency 1
• TSB rising despite intensive phototherapy, especially in the presence of hemolysis 1
• Signs of acute bilirubin encephalopathy 2

Important Considerations:

• Exchange transfusions should only be performed by trained personnel in a neonatal intensive care unit with full monitoring and resuscitation capabilities 1
• Consider intravenous immunoglobulin (0.5-1 g/kg over 2 hours) if TSB is rising despite intensive phototherapy or is within 2-3 mg/dL of exchange level 1, 2
• Monitor bilirubin levels every 2-3 hours if TSB ≥25 mg/dL 1

Common Pitfalls to Avoid

1. Failing to identify the specific antibody: The specific antibody causing hemolysis must be identified to ensure appropriate antigen-negative blood is selected 4

2. Using the infant's serum for crossmatching: Always crossmatch against maternal serum, not the infant's 1

3. Delaying treatment: HDN can progress rapidly; preparation for exchange transfusion should begin immediately when indicated 1

4. Using older blood units: Fresh blood (<7 days) is essential to minimize metabolic complications 1

5. Overlooking other supportive measures: Intensive phototherapy should be continued during preparation for exchange transfusion 1, 2

This case likely represents ABO incompatibility (mother A, baby O) or another form of alloimmunization. The positive DAT and history of jaundice in a previous child indicate a significant risk for severe hyperbilirubinemia requiring close monitoring and possibly exchange transfusion 4, 5.