Rh Immune Globulin Candidacy Triage

Principle:

All D-negative women without immune anti-D must be screened for the need to receive Rh immune globulin as soon as possible after birth.  If the mother is determined to be a candidate, then her specimen must either be screened for a large fetomaternal hemorrhage (FMH—e.g. by the E-rosette or similar technique) or directly quantitated for FMH by either the Kleihauer-Betke or flow cytometry.  The whole process must be completed so that the mother receives the entire dose of RhIG within 72 hours after delivery.

Pregnant women should have an ABO/D typing early in the pregnancy and an antenatal dose between 26-32 weeks.  Thus, at the time of birth, passive anti-D may be detected.  It is essential to know the history of RhIG administration.  In the following example, RhIG is dispensed by the Pharmacy.  If the RhIG is released by the blood bank, records should be easily obtained.

This procedure covers the hospital blood bank processes.  Close coordination between Transfusion Medicine and the obstetricians is essential for a successful Rh immunoprophylaxis program.

Abbreviations:

RhIG:  Rh immune globulin

FMH:  Fetomaternal hemorrhage

All plasma derivatives, including RhIG, are dispensed from Pharmacy.  It is the responsibility of the blood bank technologist to check the Pharmacy records for the history of RhIG administration.

For immunoprophylaxis after accidental Rh(D)-incompatible RBC transfusions, see the separate interim policy by that name.

Policy Details:

  1. Mothers with active (immune) anti-D are excluded from this procedure.  They do NOT need RhIG and to give them it is a waste of a valuable resource.
    1. If the D-negative patient has other RBC antibodies but no anti-D, then she remains a candidate for RhIG prophylaxis.
    2. RhIG has no effect for preventing alloimmunization to other RBC antigens.
  2. D-negative mothers with first-trimester abortions should be given at least 50 mcg IM RhIG dose.
    1. If clinically a large fetomaternal hemorrhage is suspected, then screen/quantitate for fetomaternal hemorrhage as detailed below.
  3. If the D-negative mother undergoes amniocentesis, version, or has had abdominal trauma, the obstetrician may request RhIG or if he suspects significant hemorrhage, fetomaternal hemorrhage quantitation and calculation of the RhIG dose as indicated below.
  4. Platelet transfusions from Rh(D) positive donors:
    1. Platelets derived from a Rh(D)-positive donor prepared by the buffy coat method or by apheresis, either suspended in plasma or PAS do not require RhIG administration.
    2. If a D-negative mother receives legacy, platelet-rich-plasma-derived platelets from a D-positive donor, it is at the discretion of the clinician to request one 300 mcg vial IM RhIG as potential immunoprophylaxis.  (Note:  PRP platelets are no longer prepared at HMC.)
  5. The cord blood of all infants from D-negative mothers without immune anti-D must be typed immediately for the D antigen upon receipt in the Blood Bank.
  6. If the D-negative mother received antenatal RhIG or if it is unclear if the anti-D detected in her blood is passive (i.e. antenatal) or active (immune), she must still be screened by this procedure.
  7. If the baby is D-negative, no further processing is necessary:  it is not necessary to give RhIG.
  8. If the baby is D-positive or if its D type is unknown, a maternal sample (EDTA-anticoagulated blood) must be screened for FMH (e.g. by the E-rosette technique).  This is done in Hematology Laboratory.
    1. The E-rosette test will detect a minimum of 10 ml of fetal RBCs.
  9. If the screen is not available, then direct FMH quantitation must be done (e.g. by either the Kleihauer-Betke staining or flow cytometry).  This is done in Hematology Laboratory.
  10. If the FMH screen is negative, then the mother should receive one 300 mcg. standard vial of IM-RhIG.
  11. If the FMH screen is positive, the dosage of RhIG must be determined by the amount of fetal bleed (expressed as “ml of fetal bleed”.)
  12. All FMH quantitation results must be calculated by a transfusion medicine physician or by the clinical service physician responsible for patient’s care and the dose of RhIG must be calculated as follows:
    1. Verify the type of RhIG available in Pharmacy:
      1. Type: IV or IM
      2. Dosage:  240/300 mcg and manufacturer’s suggested protection level:
        1. Each 240 mcg IM usually protects against 12 ml fetal bleed
        2. Each 300 mcg IM usually protects against 15 ml fetal bleed
        3. Note:  dosage depends on the origin of the pharmaceutical material.
    1. Calculate the number of vials as follows:
      1. Blood Volume in ml = (Weight in kg) X 70 ml/kg
      2. RBC Volume in ml = (Blood Volume in ml) X Hematocrit
      3. Fetal Bleed in ml = (%Fetal Bleed) X (RBC volume in ml)
      4. # Vials 300 mcg IM RhIG preparation = (Fetal Bleed in ml)/15
      5. # Vials RhIG 240 mcg IM = (Fetal Bleed in ml)/12
      6. Note:  some would add 1 additional vial to this calculation.
  13. If the calculation is performed by the Transfusion Medicine Physician, he should append a comment to the postpartum antibody screen ABID result of the mother using Medinfo Hematos IIG.
    1. If the calculation is performed by a designated individual outside Transfusion Medicine, he should document it in the patient’s medical record.
  14. The appropriate RhIG dose should be administered within 72 hours of delivery whenever possible.
    1. If greater than 72 hours post-delivery, still administer the dosage; however, the efficacy at preventing Rh(D) alloimmunization may be reduced.

Note:

  1. RhIG will only protect against forming anti-D antibodies, not any other clinically significant antibodies.
  2. If the patient is D-negative but has other clinically significant antibodies, still administer the RhIG as per the protocol above.

References:

  1. Technical Manual, Current Edition, Bethesda, MD, USA
  2. Standards for Blood Banks and Transfusion Services Current Edition, AABB, Bethesda, MD, USA