A prospective study aiming to analyze the risk of fetal and neonatal alloimmune thrombocytopenia (FNAIT) among different ethnic groups is expected to begin soon; the characteristics of the trial were recently published in the National Library of Medicine.
The study will analyse data from different regions in the United States including Arizona, Ohio, New York, New Jersey, Pennsylvania and Texas. Also included in the study are Canada and European countries like Germany, the Netherlands and the United Kingdom.
The study will include pregnant women over the age of 18 without a prior history of FNAIT. Researchers expect to quantify the frequency of human platelet antigen (HPA)-1 alloimmunization in different ethnic and racial groups, to determine if one or more groups have a significantly higher risk.
“A prospective, non-interventional, natural history study to assess the occurrence of higher FNAIT risk across a broad population of different racial and ethnic characteristics and the occurrence of HPA-1a alloimmunization in these women,” the authors wrote.
Other important outcome measures expected from the study include assessing the pregnancy outcomes (live births, premature birth, stillbirths and spontaneous abortion) in each group, and assessing the frequency of neonatal thrombocytopenia.
The expected study start date is March 2025; the authors expect to publish the final results in June 2027.
Understanding HPA distribution
The HPA antigen has two alleles HPA-1a and HPA-1b, when exposed to the HPA-1a antigen patients who only carry the HPA-1b antigen can produce antibodies against it, these antibodies can cause FNAIT during a pregnancy.
Several epidemiological studies have shown that the frequency of the HPA antigen varies significantly among ethnic groups, which explains why FNAIT is more frequent in some populations than others. In the caucasian population, for example, the frequency of the HPA-1b antigen is around 5% while in the Egyptian population it is over 20%, suggesting a higher risk of FNAIT.
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