Saturday, 17 May 2008

Clinical significance and HDFNB

Clinical Significance:

All IgG antibodies reactive by IAT 37 can cause HDFNB and HTR

All antibodies reacting only at room temp or lower are not clinically significant

Non significant antibodies may mask reactions of clinically significan antibodies.

Crossmatch antigen – negative blood where possible

Tx least incompatible blood if need is urgent

Effects of invivo antigen antibody reactions:

1. Reduced survival of transfused cells

2. Haemolytic transfusion reactions

a. Immediate - intravasacular haemolysis

b. Delayed - extravascular

3. Haemolytic disease of the fetus or newborn


a. Warm

b. Cold

c. Drug induced

Factors affecting Clinical significance

Clinical urgency of transfusion

Thermal amplitude of antibody

Antibody specificity and affinity

Frequency of corresponding antigen

Availability of compatible blood

Antigen reactivity (e.g. dosage effect)

Antibody concentration (titre) and avidity

Immunoglobulin class / subclass

HDFNB Mechanisms and Prevention


Maternal IgG antibody crosses the placenta and reacts with foetal rbc antigen of paternal origin.

Varies from mild with very little or no effect to severe anaemia, oedema, hepato-splenomegaly in foetus or newborn

In utero:

Sensitisation of fetal cells with maternal antibody

Destruction of sensitised cells by fetal RES cells in spleen and liver

Anaemia, cardiac failure, hydrops fetalis,

Bilirubin from Hb breakdown cleared by mother’s liver.

At birth:

Mild or no reactions

Anaemia, Hydrops


Maternal liver no longer available to clear bilirubin - Jaundice, Kernicterus,

Maternal immunisation

Previous transfusion or pregnancy

Crossing the placenta

Placental transport molecules on Fc portion of IgG react with Fc receptors on placental cells.


Transfusion policy for RhD neg young women

Immunoglobulin anti-D

Careful antenatal testing

Antibody monitoring,

Plasma exchange

Early delivery?

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