Edinburgh Napier University

  Objective: Severe neonatal alloimmune thrombocytopenia
(NAITP) in the Caucasian population is mainly due to a mismatch in the HPA-I epitope between mother and fetus. In August 1999 we began a 2 year study of HPA-I NAITP in pregnant women in Scotland. The aim of the study was to determine the frequency of HPA-lb homozygosity, monitor antibody (ab) levels during pregnancy, and assess the cost effectiveness of routine screening across Scotland. Design: Women were consented to the study and
all information (including scientific and clinical data) stored using Windows Access. Methods: The HPA-I antigen and antibody assays consisted of internationally validated ELISAs. Results: Of 26,506 women screened in three Scottish regions, 479 were HPAlb (1.8%): 244/13,239 (1.84%) in Edinburgh [representing the South-East]; 134/7372 (1.82%) in Aberdeen and Inverness
[representing the North-East], and 101/5895 (1.71%) in Glasgow [representing the West]. The rate ofHPA-lb women who consented to the study was around 72%. Of327 consented HPA-Ib women, 29 (8.9%) were positive for anti-HPA-Ia abo Antibody Positive pregnant women were closely monitored, with ultrasound scanning and IvIgG being employed where necessary. However,
aCcordingto our protocol, ab positive women without previous history ofNAIT were only observed and HPA-Ib platelets made available at delivery. Of26 such ab positive women, 8 (31%) had thrombocytopenic babies of whom 5 were severe [4 of these were promptly treated with I or 2 HPA-Ib platelet transfusions]. The ab litre did not appear to be related to the incidence or severity of NAITP. Furthermore, no incidence of ICH was recorded in the
study. Conclusions: Both our epidemiological data and incidence of anti-HPA_la antibody amongst HPA-Ib women concur with other studies in the Caucasian population. They also suggest that the ab titre may not be related to outcome.