Infants with fetal and neonatal alloimmune thrombocytopenia (FNAIT), a disorder in which a pregnant woman develops alloantibodies against the platelets of a fetus, typically have very low levels of circulating platelets. Platelets are red blood cells needed to form blood clots during bleeding episodes.
Without sufficient levels, bleeding episodes may occur for an extended, and sometimes dangerous, period of time.
What is platelet crossmatching?
Because of the low levels of circulating platelets in FNAIT, platelet transfusions are often necessary.
You may have heard of the concept of “platelet crossmatching”. This involves checking the compatibility of the platelets from a donor with the blood of a recipient to reduce the chances of unwanted transfusion reactions and to ensure that the platelets transfuse survive after transfusion.
While this approach may be recommended in certain medical conditions, it is not generally recommended in FNAIT for several well-documented reasons.
Why platelet crossmatching is not recommended
There are a number of characteristics of FNAIT that make platelet crossmatching not ideal.
In platelet cross-matching, the goal is to identify platelet compatibility, which is often accomplished by avoiding reactions arising from the interaction between antigens and antibodies. Unfortunately, in FNAIT, it is precisely the interaction between maternal antibodies and fetal platelet antigens that give rise to the complications typically associated with FNAIT. Thus, platelet cross-matching fails to address one of the primary problems in FNAIT.
Read more about FNAIT testing and diagnosis
Furthermore, even if blood bank specialists mount a concerted attempt to search for platelets that are specifically negative for the specific antigen that reacts with the maternal antibodies produced, these are extraordinarily rare and represent a significant hurdle to platelet crossmatching being a solution to FNAIT.
Another massive problem with the idea of using platelet crossmatching in FNAIT is that, even if such platelets are transfused, maternal alloantibodies abnormally produced in FNAIT are primed to continue to destroy fetal platelets. Eventually, the transfused crossmatched platelets are depleted, and we are back to square one.
The destruction of platelets in FNAIT is not completely dependent on antigen compatibility.
What you can do instead
For all these reasons, backed up by solid scientific research, platelet crossmatching is not recommended in FNAIT. While this approach may not be effective, there are a number of tried and tested methods that are likely to produce positive results, such as the use of intravenous immunoglobulins, corticosteroidsand intrauterine platelet transfusions.
If these approaches are unfamiliar to you, speak to your doctor about the treatment solutions that are available to you and your child. Many of the modern approaches in dealing with FNAIT can reduce the complications associated with this condition.
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