Transcript Guidelines for blood grouping and red cell antibody

Guidelines for blood grouping
and red cell antibody testing
during pregnancy
Transfusion Medicine, BCSH
INTRODUCTION
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ABO Rh D-typing and antibody screen tests on
the sera of the pregnant women are performed for
the protection of the mother and the identification
of HDN
The guidelines are addressed to the hematology
unit undertaking such antenatal testing.
It is accepted that samples should be tested only
when it is likely that results could influence the
clinical management of the pregnancy.
OBJECTIVES
The objectives of routine serological testing are:
a) Identify pregnancies at risk of fetal and neonatal
HDN
b) Identify RhD-negative women who need anti-D Ig
prophylaxis
c) Provide compatible blood swiftly for obstetric
emergencies.
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OBJECTIVES
2) When red cell ab are present, the purpose of f/u
serological tests are:
a) identify the fetus that may need treatment before term
b) predict infants who are likely to require treatment for
HDN in the neonatal period
c) identify any additional red cell allo ab developing during
the course of the current pregnancy.
d) identify additional maternal ab induced by intrauterine red
cell transfusions
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Testing protocols
1) All pregnant women
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The first antenatal examination at booking is
usually at 10-16 wks POA- test for ABO and
RhD gp and presence of red cell alloab
When an ab screen is +, further testing sh be
carried out to determine ab specificity and
significance.
Subjects who have weak RhD blood groups are
RhD + & do not form immune anti-D
Cont:
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It is essential that pt with ab of clinical
significance sh be referred for advice to a
specialist at the earliest oppurtunity
Testing for ABO immune ab in the maternal
serum is not recommended as their presence
neither predicts ABO HDN nor causes problems
in utero
Testing Protocols
2) No red cell ab detected at booking
 They sh be retested once during 28-36 wks
gestation.
 Rh D-negative women sh have at least 2 tests
performed during this period, one of which sh be
at 34-36 wks(optional)
Cont:
3) Red cell ab present at booking
 If have previous affected baby by HDN, they sh
be referred early to a specialist unit for advice
before 20 wks gestation for assessment for fetal
haemolysis, irrespective of ab level.
 This will enable the need for amniocentesis and/
or fetal bl sampling and intrauterine transfusion
 Neither the specificity nor the level of maternal
rbc ab can precisely predict outcome for the
infant.
Cont;
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When an ab or abs are detected at 10-16 wks of
gestation, subsequent testing sh be done to
determine the specificity, concentration , origin
and level of ab or abs and the likelihood of HDN
Anti-D, anti-c & anti-Kell are abs most often
implicated in causing moderate to severe HDN
Paternal Sample
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When a clinically significant ab capable of
causing HDN is present in a maternal sample,
testing the partner’s phenotype provides useful
information to predict the likelihood of a fetus
carrying the relevant rbc ag
Women with anti-D
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If have anti-D detected, they sh be tested at least
until 28 wks and every 2 wks thereafter to
monitor the level of anti-D and to identify any
additional abs that might develop
When intrauterine transfusion are given, the
maternal serum sh be screened for additional abs
prior to each transfusion
Cont;
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Titration of anti-D does not closely correlate with
the occurrence of HDN
Anti-D quantification using the national anti-D
std is more reproducible and correlates more
closely with the likelihood of HDN
An increase of anti-D level by 50% or > over the
previous level indicates a significant rate of
increase, irrespective of period of gestation
Cont:
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Anti-D is the rbc alloab most frequently
responsible for serious HDN.
Generally the significance of the anti-D level is as
follows,although exceptions can occur.
Anti-D < 4iu/ml
HDN unlikely
Anti-D 4-15 iu/ml
moderate risk of HDN
Anti-D > 15 iu/ml high risk of hydrops fetalis
Women with rbc alloab other
than anti-D
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All non-D abs reacting with indirect antiglobulin
test sh be titrated against RBCs heterozygous for
the corresponding ag
Anti-c and ab within Kell bld gp system with or
without other abs are the non-D abs most likely to
cause haemolytic disease severe enough to
warrant antenatal intervention
They sh be retested with the same frequency as
women with anti-D.
Cont;
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For all other abs reactive by IAT, retesting once at
28-34 wks provide enough info to determine mx
of pregnancy
Significant titres likely to cause HDN are a titre
of 32 or > except for Kell-related abs which may
affect the fetus regardless of the titre
In general, anti c, -K,-e,-Ce, Fya, Jka and –Cw
have greatest potential to cause HDN.
Cont;
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Anti- Lea, -Leb, -Lua, -P, -N, -Xga and high-titre
low-avidity abs eg; Knd have not been implicated
in HDN.
Action at time of delivery
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Maternal samples and a cord blood sample sh be
taken at delivery from Rh-negative women with
no immune anti-D
The cord bld sample sh be used to determine the
infant’s Rh D grp,can identify the women who
must receive prophylactic anti-D Ig
When the infant is RhD positive, the DCT sh be
done on the cord rbc.
Cont;
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This is to identify HDN due to anti-D developing
in late pregnancy .
A positive DCT has been shown to be a good
predictor of HDN
A test should be done on the maternal bld sample
to establish the size of the fetomaternal bld so that
additional anti-D Ig may be given when required
Cont;
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DCT sh be done on cord rbc when the maternal
serum contains clinically significant rbc abs
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if +ve, rbc eluate can identify the rbc ab
specificity
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Wherever possible, the rbc from the cord sh be
tested for the corresponding rbc ag
Cont;
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All infants born to mothers who have clinically
significant abs in their serum sh be closely
observed for the evidence of HDN during the
next 48-72h of life
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They sh not be discharged earlier unless
subsequent follow-ups is arranged
Testing of bld samples fr women who have
received a/natal prophylaxis with anti-D Ig
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Antenatal prophylaxis with anti-D IgG is
practised in some regions.
Passive anti-D may be detectable in the serum by
enzyme tests as well as by IAT for up to 12 wks
or more after the administration of anti-D IgG.
Testing of maternal serum for anti-D prior to the
second prophylactic dose or post-delivery may be
confusing and isnot recommended as passive
anti-D cannot be differentiated fr alloimmune
anti-D
Cont;
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When non-D abs are present in a woman who
received antenatal anti-D IgG prophylaxis, the
testing protocol already described for this gp of
patients sh be followed