UnityPoint Des Moines Laboratory
Immunhematology
1200 Pleasant Street
Des Moines, Iowa 50309
Questions regarding Rh Immune Globulin and what testing is required: to be determined with pathology direction and your own sites policies.
AABB 29th Standards:
5.30 Rh Immune Globulin
The transfusion service shall have a policy for Rh Immune Globulin prophylaxis for Rh negative patients who have been exposed to Rh positive red cells.
5.30.2 Women who are pregnant or who have been pregnant recently shall be considered for Rh Immune Globulin administration when all of the following apply:
1. The woman’s test for D antigen is negative. A test for weak D is not required.
2. The woman is not known to be actively immunized to the D antigen.
3. The Rh type of the fetus/infant is unknown or the type of the fetus/infant is positive when tested for D or weak D. Weak D testing is required when the test for D is negative.
5.30.3 There shall be a process to ensure that an adequate dose of Rh Immune globulin is administered.
5.30.4 Rh Immune Globulin Shall be administered as soon as possible after exposure.
5.30.5 Patients who have received Rh Immune Globulin shall be evaluated to determine the need for additional treatment.
What does that mean?
Who is a candidate?
If anti-D is found in the patient antibody screen/antibody ID, is it passively acquired from the drug or is it immune in nature? Do we need to give the patient more Rh Ig? How do we know? Titer of <8 is usually drug. Titer of 8 is likely immune anti-D.
Have we given an effective dose to prevent alloimmunization?
Mothers sample: ?# weeks gestation, ?is pregnancy continuing, ?is infant cord testing available or unknown, ?is trauma/bleed suspected.
For routine 28 week gestation antenatal, so during pregnancy:
Type and screen, so includes ABO, RH with Weak D for any Rh negative, antibody screen.
If mother is Rh negative AND antibody screen is negative for anti-D: Routine practice is to give one 300 microgram dose just in case infant is Rh pos.
At trauma or suspected bleed during pregnancy up to 20 weeks gestation:
Type and screen, so includes ABO, RH with weak D for any Rh negative, antibody screen.
If mother is Rh negative AND antibody screen is negative for anti-D: Routine practice is to give one 300 microgram dose.
For pregnancy at or greater than 20 weeks gestation and pregnancy continuing:
Type and screen, so includes ABO, RH with weak D for any Rh negative, antibody screen.
If mother is Rh negative AND antibody screen is negative for anti-D, and fetalscreen is negative: Routine practice is to give one 300 microgram dose. When fetalscreen is positive, Flow HbF is done and calculation performed.
KEY point: Perform antibody screen if pregnancy is continuing to look for developing antibodies including anti-D.
At delivery and greater than 20 weeks gestation so pregnancy is not continuing:
KEY point: Sample requirement: POSTPARTUM
ABORH with Weak D for any Rh negative, and a qualitative fetalscreen is our practice/policy. (As long as infant cord testing is both DAT negative and Rh positive or weak D positive). UPDM does not routinely perform antibody screen at delivery or termination of pregnancy per our policy. Why? There is no harm in giving Rh Ig to a mother with immune anti-D.
If fetalscreen is negative, give one 300 microgram dose. If fetalscreen is positive OR if infant is DAT pos ( which invalidates the fetalscreen findings) , the quantitative Flow Cytometry Hgb F is performed as a reflex. We use flow cytometry hemoglobin F at UPDM as quantitative. Others may use Kleihauer Betke fetal stain.
KEY point: Fetalscreen rosette test is only valid at 20 weeks. It is qualitative only. So if fetus is in distress or possibly in danger at less than 20 weeks, flow cytometry HbF is needed to quantitate bleed.
KEY point: Fetalscreen rosette test is valid only when infant is not DAT positive. A DAT positive infant’s cells may have been cleared from mother’s circulation quickly so the fetalscreen could be falsely negative.
Mother / Infant / Flow cytometry requiredRh negative / Rh is Weak D positive
DAT negative / Yes ( infant is WKD)
Rh negative / Rh negative with Weak D undetermined due to
Positive DAT / Yes ( pos DAT)
Rh negative / Rh positive
DAT positive / Yes ( pos DAT)
Calculation for dose when there is a positive fetalscreen and flow cytometry Hgb F is performed:
(% fetal cells X 50 = # mls of fetal blood present in mother
Divide that #mls by 30 mls which is the whole blood covered by one dose.
Round up if number to right of decimal is 5 or more and round down if number to right of decimal is less than 5, and add one dose.
Example: 0.13% x 50 = 6.5 mls 6.5 mls / 30 mls = 0.22 doses Give one dose.
Example: 0.68% x 50 = 34 mls 34 mls / 30 mls = 1.13 doses Give two doses.
Jobaid: RhIG Questions 121614