BB exam 4 (minus 1): HDN, Immune mediated hemolysis and the DAT, Transfusion rxn and massive transfusion

what isotype is responsible for hdn?

IgG

HDN abs are directed toward s the ags inherited from whom?

father of baby

what are the two most antigenic systems for HDN?

D and Kell

What are the most common abs for HDN?

anti-K,c,Fya

what trimester are IgG actively transporting?

2nd trimester

For HDN, IgG are transported via:

Fc portion

what subclasses of IgG are more efficient in crossing the placenta?

IgG1 and IgG3

what do anti-K do to fetal erythropoietic cells?

suppress them in addition to hemolysis

describe hemolysis in HDN?

maternal IgG abs attach to fetal rbcs

sensitized rbcs removed by macrophages of the spleen

destruction of the rbc exceeds production by the bm

resultant anemia

what does anemia cause in the fetus during HDN?

erythroblasosis fetalis

when the fetus has severe anemia during HDN, where does erythropoiesis occur?

BM, liver and spleen

What two organs of the fetus enlarge with HDN?

liver and spleen - hdn causes severe anemia, resulting in the liver and spleen to pick up some erythropoiesis responsibilities

what causes hypoproteinemia in a fetus with HDN?

caused by decreased hepatic production of plasma proteins

a fetus with severe anemia during HDN can have a (high/low) output cardiac failure

high

when can a fetus have hydropis fetalis?

18-20 wks gestation

T/F: after the baby is born, rbc destruction stops

false - it continues post delivery

bilirubin is (increased/decreased) for fetus with HDN?

increased - indirect bili

when fetus has excess indirect bili, what happens to it?

indirect bili travels through placenta to maternal liver, where it's conjugated to direct bilirubin and excreted by mother's system

T/F: newborn babies have a sufficient amount of glycuronyl transferase

false - can lead to jaundice or kernicterus

what do you do for saline testing?

dont add LISS; incubate for 60 minutes

what is considered a significant titer for maternal abs for HDN?

16-32

also significant if the titer starts to rise

When do you repeat an antibody titer during pregnancy for HDN?

repeat at 18-20 wks

what is step 1 of pre-natal testing?

maternal evalulation

what tests are a part of maternal evaluation for pre-natal testing?

maternal ABO and Rh typing

antibody screen

antibody ID

antibody titer

patient history

paternal phenotyping

what is step 2 of pre-natal testing?

fetal evaluation

how do you test fetal bilirubin?

amniotic fluid evaluation

spectrophotometric scan

look for change in optical density

record the change in density at 450nm

What is plotted on the Liley graph?

The change in optical density of amniotic fluid vs gestational week

good for bilirubin

gives an indirect prediction of fetal anemia

what gives an indirect prediction of fetal anemia?

bilirubin evaluation and liley graph

if baby's bili is in zone I of liley graph, what does that mean?

mild or no disease

if baby's bili is in zone II of liley graph, what does that mean?

moderate HDN

if baby's bili is in zone III of liley graph, what does that mean?

severe and often fatal HDN

When is optical density highest for fetus?

2nd trimester - should decrease from there until delivery

What indicated fetal distress when looking at a Liley graph?

increasing of unchanging optical density

what OD test can you perform starting at week 14 of gestation?

Queenan

what OD test can you perform starting at week 27 of gestation?

liley graph

at what wk should a mother take her first dose of RhIg?

28 wks

from where can you take a sample of fetal blood?

umbilical vessel in the umbilical cord

what tests can you perform from cordocentesis?

hb

hct

fetal blood type

ag typings

DAT

what is step 3 of pre-natal testing?

fetal intervention (trying to treat the baby)

What step of pre-natal testing will an intrauterine transfusion be performed?

step 3 - fetal intervention

what are some reasons to perform an intrauterine transfusion?

amniotic fluid results are in high zone II or zone III

cordocentesis sample has hb less than 10 g/dL

fetal hydrops is noted on ultrasound exam

how often are intrauterine transfusions performed?

every 2-4 wks until 34-36 wks gestation

What are two cons to intrauterine transfusions?

can suppress fetal bm

can cause trauma to placenta - may cause rise in maternal ab titer

What type of blood is given during intrauterine transfusions?

Group O packed rbcs with AB plasma

irradiated

CMV-

HbS-

Ag-

less than 7 days old

crossmatch compatible with maternal serum

what is step 4 of pre-natal testing?

neonatal treatment

Why use UV light on neonates?

converts unconjugated bili to bilverdin

T/F: blood warmers are not necessary for neonatal exchange transfusion

false

what is the hct range necessary for neonate transfusion?

45-60%

most important serologic test for diagnosis of HDN

DAT

serologic testing you can do on a newborn:

ABO grouping

Rh Typing

DAT

Elution

what can cause a false negative Rh?

prozone

when might you do an elution?

with a + DAT

why might cord blood be taken from a newborn?

its taken on all newborns

what is a possible contaminant of cord blood?

wharton's jelly

hdn with abo can happen with (1st/2nd) pregnancy

1st

HDN: Disease predicted by titers (Y/N):

ABO

Rh

ABO: No

Rh: Yes

HDN: IgG (Y/N):

ABO

Rh

ABO: Yes (anti-A,B)

Rh: Yes (anti-D)

HDN: Bili at birth:

ABO

Rh

ABO: normal

Rh: elevated

HDN: Anemia at birth:

ABO

Rh

ABO: no

Rh: yes

HDN: Phototherapy:

ABO

Rh

Yes for both

HDN: Intrauterine transfusion

abo

rh

abo: no

rh: sometimes

HDN: Spherocytosis

ABO

Rh

abo: yes

rh: rare

how many mothers are sensitized without prophylaxis if theyre Rh- and baby is Rh+?

16%

what is the mechanism of RhIg?

attaches to fetal cells circulating in mother

ab coated cells are removed by macrophages in maternal liver

ag sites are now unavailable for dendritic cells to present ag to T helper cells

when do you have your first Rhogam shot?

28 wks

how many mls of fetal blood does RhIg protect against?

30mLs

what test is performed if theres a massive fetomaternal hemorrhage?

kleihauer-betke test

calc for rhig in large fetal bleeds

fetal cell% x 50 = fetomaternal hemorrhage in mL

single dose = 30ml

0.5 = round up

always add 1

qualitative screen in determining FMH

rosette test

detects 10 mL or more

if neg, single dose

if pos, indicates larger FMH

quantitative testing for determining FMH

flow cytometry

KB test

Types of AHG reagents

polyspecific

anti-IgG (monospecific)

Anti-C3b, -C3d (monospecific)

what is the most important complement antibody?

anti-C3d

what animals are AHG abs made from?

murine or rabbits

what part of the ab binds to the rbc?

Fab region

what part of the ab is bound by AHG?

Fc region

what is sensitization?

when an ab binds to an rbc

what isotype is AHG?

IgM

What isotype does AHG bind?

IgG

what are the only two complement abs used?

anti-C3b and anti-C3d

what can result in neutralization of the reagent and false negative results?

inadequate washing

What is in Check cells?

IgG sensitized cells

Do you want a + or - reaction with check cells?

positive; if negative, test results are invalid

what methods do you use check cells for?

only tube method - not gel or solid phase methodology

what does IAT stand for?

indirect antiglobulin test

IAT: (In vivo / in vitro) sensitization

in vitro

used to determine presence or absence of allo- or autoantibodies in plasma or serum

IAT

what does DAT stand for?

Direct antiglobulin test

DAT: (in vivo / in vitro) sensitization

in vivo

what test should you perform if person comes into hospital with no bleeding but with hemolysis?

DAT

what test should you perform if a neonate has too much jaundice?

DAT

What is DAT used to detect?

hemolytic transfusion reactions (immediate or delayed)

Hemolytic disease of the newborn (HDN)

Autoimmune hemolytic anemia

drug induced hemolysis

how many IgG molecules should be on your rbc before it can be recognized by DAT?

100-500 IgG molecules / rbc

how many C3d molecules should be on your rbc before it can be recognized by DAT?

400 - 1100

What can cause a false negative with DAT?

cells sitting for prolonged periods prior to or after the addition of antisera

what can cause a false positive with DAT?

spontaneous agglutination due to heavy coating of rbcs (use control)

C3 may be detected if using clotted sample - use fresh EDTA sample

DAT patient history - important elements:

recent blood or component transfusion

drugs

HPC (bm/stem cell) or solid organ transplant

Immune globulin

how long after primary sensitization does the DAT show up +?

7-10 days after

how long after secondary sensitization does the DAT show up +?

1-2 days after

what are passenger lymphocytes?

when you take an immunosuppressive drug before a bm transplant, you lose your entire immune system. the tranfused lymphocytes come into body and take over immune response

passenger lymphocytes can produce antibodies against:

recipient rbc ags