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Usefulness of maternal anti‐ HPA ‐1a antibody quantitation in predicting severity of foetomaternal alloimmune thrombocytopenia
Author(s) -
Sainio S.,
Javela K.,
Tuimala J.,
Koskinen S.
Publication year - 2013
Publication title -
transfusion medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.471
H-Index - 59
eISSN - 1365-3148
pISSN - 0958-7578
DOI - 10.1111/tme.12018
Subject(s) - neonatal alloimmune thrombocytopenia , medicine , antibody , platelet , immunology , pregnancy , predictive value , gastroenterology , obstetrics , fetus , biology , genetics
Summary Objective To study the clinical usefulness of maternal anti‐ HPA ‐1a antibody levels in predicting severe foetomaternal alloimmune thrombocytopenia ( FMAIT ). Background Recent studies using an international anti‐ HPA ‐1a standard have shown a correlation between maternal antibody levels and neonatal thrombocytopenia. Cut‐off values for identifying high‐risk pregnancies have also been suggested. Materials In 1986–2010, HPA ‐1a alloimmunisation was confirmed in 84 women with 129 pregnancies. Maternal samples were obtained at delivery and during subsequent pregnancies. Anti‐ HPA ‐1a was quantified using a MAIPA assay with a detection limit of 0·8 IU mL ‐1 ( WHO reference serum 03/152). Antibody levels were compared with the severity of neonatal disease in the index and in the subsequent pregnancies. Results In the index cases, the correlation between an anti‐ HPA ‐1a level and neonatal platelet count did not reach statistical significance ( n = 77, P = 0·074). However, the platelet counts and antibody levels in cases with cutaneous ( n = 45) or intracranial haemorrhage ( n = 7) were significantly different from cases with no evidence of bleeding ( n = 20). In the subsequent pregnancies, there was a stronger association between the second trimester anti‐ HPA ‐1a level and the foetal platelet count ( n = 16, P = 0·046). The positive predictive value of the maternal antibody level for a foetal platelet count <20 × 10 9 L ‐1 was 90%, but the negative predictive value only 31%. Conclusion Although a higher anti‐ HPA ‐1a level correlated with a more severe neonatal disease, barely detectable antibody levels were also observed in severely affected pregnancies. Cut‐off values with sufficient sensitivity and specificity to identify these foetuses could not be found. A previous obstetric history still remains the most useful predictive parameter for severe FMAIT in clinical practice.