Immunohematology - HDFN

HDFN

fetal or newborn RBCs are destroyed by maternal IgG

fetomaternal hemorrhage

alloimmunization may occur when fetal cells escape into the maternal circulation as a result of a _____

anemia

what is the concern with HDFN before birth?

hydrops fetalis

RBC destruction leads to anemia, RBC count decreased and production increases including into liver and spleen, RBC production causes spleen and liver to enlarge, albumin production by liver decreases in response to portal hypertension

bilirubinemia

what is the major concern with HDFN after birth?

bilirubinemia

neonates cannot conjugate bilirubin or oxidize it into urobilinogen, unconjugated bilirubin binds to albumin and then to tissues (jaundice), bilirubin binds to tissues of the CNS resulting in permanent brain damage (kernicterus)

ABO HDFN

most common type of HDFN, most often mother has type O blood and baby has A or B, antibodies are naturally produced

ABO HDFN

production of mild symptoms is possible, A or B substances in tissue may neutralize antibodies, fetal RBC antigens poorly developed, fewer A and B antigens sites of fetal RBCs

ABO HDFN

usually not severe, can develop into hydrops or be fatal (rare), jaundice possible, spherocytes, phototherapy can treat jaundice

phototherapy

initial treatment for hyperbilirubinemia, uses fluorescent blue light that converts bilirubin into Z lumirubin and Z-E bilirubin via photooxidation and photoisomerization that are excreted in the bile and urine

alloantibody HDFN

fetomaternal hemorrhage, maternal antibodies form against paternally derived antigens, subsequent pregnancy: maternal IgG Abs cross placenta, maternal antibody attaches to fetal RBCs, fetal RBC hemolysis

RHD HDFN

most severe, D neg women are sensitized during first pregnancy with D pos baby, subsequent pregnancies are affected; severe jaundice and/or anemia, exchange transfusion may be necessary

exchange transfusion

replacement of 1-2 whole blood volumes, corrects anemia without expanding the blood volume, removes newborns RBCs and replaces them with antigen neg cells, reduced bilirubin and maternal antibody

RhD immune globulin (RhIG)

given to prevent RhD HDFN, prevents alloimmunization in D neg mothers, prevents formation of anti-D antibody

IgG

any _____ can cause HDFN

anti-c, anti-E, anti-K

_____ antibodies are common causes of non-RhD HDFN

prenatal testing

identifies D neg women who are candidates for RhIG and women with antibodies capable of causing HDFN

antibody titration

helps determine whether certain procedures should be performed

ultrasound

can detect fetal anemia

amniocentesis

amniotic fluid is scanned spectrophotometrically from 350-700nm, change in optical density above baseline at 450nm is a measure of bilirubin

liley graph

the optical density is plotted on a _____ using gestational age

cordocentesis

fetal blood sample taken for Hgb and Hct testing, bilirubin testing, RBC genotyping, can be used for intrauterine transfusions in cases of severe HDFN

intrauterine transfusion

correctsw anemia and prevents heart failure; group O neg RBCs, collected within 7 days, irradiated, neg for CMV, leukoreduced, crossmatch compatible with mother’s plasma, neg for Hgb S

fetal genotyping

fetal DNA can be typed using maternal plasma during second trimester, predicting this could avoid amniocentesis or cordocentesis if the fetus lacks the antigen

postpartum testing D testing

all infants born to D neg mothers are tested, through weak D antigen

postpartum ABO testing

only forward grouping is performed, cord blood washed to remove wharton’s jelly

postpartum DAT testing

elution may be necessary if test is pos and mothers antibody has not been identifiedw

lui freeze thaw

what is the most common elution method for DAT testing postpartum

rosette test

most common screening for fetomaternal hemorrhage; uses postpartum maternal specimen incubated with anti-D antibody, D pos indicator cells, rosettes observed under microscope

kleihauer-betke test

quantifies fetomaternal hemorrhage and calculates additional doses of RhIG, based on the fact that fetal hemoglobin is resistant to acid and adult hemoflobin is not resistant to acid

flow cytometry

accurate fetal cell counts can be performed using _____, a maternal blood sample is treated with reagents that label only the D pos cells

hemoglobin F

cells can be labeled with an antibody to _____, can quantify FMH in D compatible pregnancies, can lead to erroneous results due to persistence of HgF