Published online 28 April 2008
Haematologica, Vol 93, Issue 6, 870-877 doi:10.3324/haematol.12515
Copyright © 2008 by Ferrata Storti Foundation
Mette Kjær Killie1 ,
Anne Husebekk1,2 ,
Jens Kjeldsen-Kragh3,4 ,
Bjørn Skogen1,2
Haematologica, Vol 93, Issue 6, 870-877 doi:10.3324/haematol.12515
Copyright © 2008 by Ferrata Storti Foundation
Original Article |
A prospective study of maternal anti-HPA 1a antibody level as a potential predictor of alloimmune thrombocytopenia in the newborn
1 Department of Immunology and Transfusion Medicine, University Hospital of North Norway, Tromsø
2 Department of Immunology, University of Tromsø
3 Department of Immunology and Transfusion Medicine, Ullevål University Hospital, Oslo and
4 Faculty Division Ullevål University Hospital, University of Oslo, Norway
Correspondence: Mette Kjær Killie, Department of Immunology and Transfusion Medicine, University Hospital of North Norway, 9038 Tromsø, Norway. E-mail:mette.kjaer.killie{at}unn.no
Background: Neonatal alloimmune thrombocytopenia is most commonly due to transplacental passage of maternal anti-HPA 1a antibodies. A prospective study was carried out to evaluate the pattern and quantity of maternal anti-HPA 1a antibodies in order to predict the level of thrombocytopenia in the neonates.
Design and Methods: A monoclonal antibody immobilization of platelet antigen assay was used to detect antibodies in maternal samples from 1,990 HPA 1bb women. HLA DRB3*0101 typing was performed in all immunized women by sequencing the HLA DRB3 gene when present.
Results: Primary immunization more often took place in connection with delivery than during the first pregnancy. There was a strong correlation between maternal antibody levels and the platelet counts in the newborn (R2=0.49, p<0.001). A maternal antibody level above 3.0 IU/mL measured in gestational week 22 or 34 had a diagnostic sensitivity and specificity of 93% and 63%, respectively, for predicting the grade of neonatal thrombocytopenia. The women who were negative for HLA DRB3*0101 had significantly lower anti-HPA 1a antibody levels than those who were HLA DRB3*0101 positive (p<0.007). In contrast to primigravida, in whom anti-HPA 1a antibody levels increased during pregnancy, the antibody level decreased in 92 of 147 women who had been pregnant previously (P92 or more of 147 = 0.003). The anti-HPA 1a antibody level regularly increased after delivery.
Conclusions: Maternal anti-HPA 1a antibody levels in weeks 22 and 34 of pregnancy are good predictors of the degree of thrombocytopenia in the newborn both in the first and subsequent pregnancies. Most mothers became immunized at the time of delivery.
Key words: anti-HPA 1a, neonatal alloimmune thrombocytopenia.
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Haematologica 2008 93: 805-807.
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