HDFN Flashcards
what immunoglobulin class can cross the placenta
IgG
Rh
Kell
Kidd
Duffy
Xga
P
what are the two things that can be caused by HDFN
anemia
erythropoeisis “Erythroblastosis fetalis”
what are some foreign antigen stimulus to red cell antigen?
previous transfusions
pregnancy
- fetomaternal hemorrhage
- occurs during delivery
- small amount of blood (<30 mL)
- chances of bleed increase trauma, invasive procedures
factors that affect maternal antibody production
amount of blood
immunogenicity of antigen
previous exposure
maternal immune response
ABO compatibility
why is an Rh HDN significant?
during the first pregnancy, the delivery is the first sensitizing event
when delivering the second baby there is a chance for a mild HDN as the second exposure will cause the titre to rise
pathogenesis of severe cases of HDFN
profound anemia
hepatosplenomegaly
hypoproteinemia
cardiovascular failure
“Hydrops fetalis” severe edema
sever cases of HDFN post partum
anemia
hyperbilirubinemia
hemolysis continues post partum
severe HDFN blood groups inlude
all Rh antibodies
Kell
Duffy
Kidd
mild HDFN blood groups include
ABO
Duffy - Fyb
not associated with HDFN
Lewis, P, I
most common HDFN blood groups
ABO Rh Kell
rare HDFN blood groups
Kidd, Duffy, MNS, others
disease at birth caused from ABO blood group
no anemia
no jaundice but increased bilirubin
spherocytes on smear
what is the source of RhIG
human source acquired from pooled plasma containing anti-D
- using ion exchange chromatography
- solvent detergent to destroy lipid enveloped viruses and ultrafiltration steps (removing non enveloped viruses)
T or F RhIG can be delivered IV or IM
True
what is the use of RhIG
used for the prevention of anti-D production in pregnancy and given to Rh neg females
involve inhibiting the adaptive immune system by
- masking the epitope of D antigen
- increasing rate of removal of D pos infant cells by opsonization
- FcyRIIB receptor inhibition of B cells
when is RhIG given to Rh neg females
28 weeks gestation
- will remove Rh pos fetal cells that enter the maternal circulation prior to giving birth
<72 hrs post delivery of Rh pos or Weak D pos infant
- removes fetal cells from circulation at the time of delivery
additional dose may be given throughout pregnancy
what is the standard dose of RhIG
300 ug will clear 30 mL of whole blood an 15 mL of packed cells
what is the half life of RhIG
23-26 days and can be detected up to 8 weeks in patients following injection
- can have allergens so consent is needed
- it is not effective if active anti-D is present
- it does not prevent antibody production
other uses of RhIG
Rh incompatible transfusions
- given to Rh neg females of child bearing potential <45yrs who received Rh pos blood
Treament for idiopathic thrombocytopenic purpura
prenatal testing follow up
if antibody screen pos
- perform Ab ID with panel
- perform titration
- antigen type mother and father
all verbally reported to physician
what titre is significant for IgG antibodies
titre of 16 up
any titre of anti-K is significant
significant rise in titre - greater than two tubes
what can cause a discrepancy in cord testing
Wharton’s jelly
what is test is significant when testing baby
DAT
what two methods are used to ID Ab or Ag
elution - removal of Ab for ID
dissociation - removal of Ab for antigen typing
what is a fetal bleed screen (rosette test)
detects >30mL of Rh pos fetal cells that entered maternal circulation
- performed on maternal sample 1 hour after delivery
- if mother eligible for RhIg - FBS
- pos result means addition RhIg is requires
screening test
what is the Kleihauer Betke test
determines how much Rh pos blood has entered maternal circulation
determine how many extra doses of RhIG is required
quantitates how many fetal cells there are
procedure of Kleihauer betke
peripheral blood smear is treated with acid, fetal cells will remain intact because of high concentrations of hemoglobin F while adult cell is eluted out.
what is the equation for vials of RhIg
% fetal cells x maternal blood volume (~5000 mL) / 30 mL
procedure of rosette test
maternal 3% incubated with monoclonal anti-D at room temp, Ab will bind to infant Rh pos cells
after washing off unbound Ab indicator cells added R2R2.
