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Neonatal Allo Immune Thrombocytopenia


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My first post in your forum. Congratulations and keep up the good work.

I would like to know your clinical prctice regarding diagnosis and management of NAIT.

1. Which combination of clinical symptoms and lab results are suggesting NAIT, taking into consideration that current anti platelet Ab detection has a high rate of false negatives?

2. What kind of trnsfusion product do you use. Random donor platelets, do you have typed platelets, do you perform mother platelet apheresis?

3. Have you come across any non-responders?

4. What about genetic councelling to parents of NAIT neonates?

Dimtris Anastasiou

Neonatology Resident

Athens, Greece

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We use IVIG and any available platelet transfusion. We send blood from both Parents to the Blood center of Wisconsin http://www.bcw.edu/bcw/index.htm. They are the best in the USA. May need 2-3 IVIG infusions.

Thank you for your feedback. Do you always rely on a positive flow cytometry and/or a positive glycoprotein-specific assay or the diagnosis is sometimes clinical?

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Initial diagnosis is clinical - mother's platelets are normal and the baby has low platelets usually less than 40k and all coagulation tests are normal. Transfused platelets are destroyed and the count usually goes down rapidly. It is difficult to obtain mother's platelets for immediate use. We do not have access to flow cytometry. The blood center of Wisconsin has a good website and are very helpful with the labs and any clinical interpretation.

Regards

Shantharama

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Hi,

NAIT usually presents as petechiae in a well newborn, who then shows low platelet counts; usually quite profound, in 20-40,000. Mother's platelet count is normal with no h/o any auto-immune disorder. Subsequent tests from baby and both parents confirm NAIT with baby having anti-platelet antibodies, transferred across from mother (very similar to Rhesus disease).

If the baby's platelet counts respond to platelet transfusions, then I prefer not to give IVIG as later is a blood product pooled from multiple donars. NAIT is a self limiting disorder and baby's platelet counts improve after few weeks as long as we support that with platelet transfusions, there is no rush to expose the baby to a blood product from multiple donars.

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The reason for posting this thread is that we have had in our unit a neonate who presented with severe bleeding and finally died. He did not respond to random donor platelets with laboratory confirmed platelet count elevation although bleeding was controlled after each transfusion. He did not respond even after mother donated platelets.

Blood collected from both parents and baby was sent for MAIPA which failed to reveal anti-HPA Abs in mother's serum, although genotyping showed an incompatibility in HPA-15b (baby and father positive, while mother negative). HLA cl I Abs were found but they are not considered the main anti-HPA lysing platelets. We have come to the conclusion that the negative MAIPA result must have been a false negative due to epitope competition between monoclonal Abs and maternal anti-HPA Abs.

A lot of questions arise:

1. Would it help to repeat the test using a different monoclonal Ab? Is that technically feasible for the HPA-15b antigen? Is the test reliable 5-6 months after the event or the titer falls rapidly after birth?

2. Is there an explanation for non-responders babies with NAIT? Could we attribute the non-response to maternal platelet destruction during handling-irradiatio?

3. What genetic counceling would you offer? E.g. in the next gestation amniocyte genotyping for HPA-15 in the baby?

Thank you Shantharama Karanth and raviagarwal for pointing out that diagnosis is clinical and you cannot wait or rely on lab results to confirm it! It is very important to remember this when dealing with such babies.

Here you can download the most complete review on the laboratory evaluation of NAIT I found online.

Any feedback, suggestions or answers to the questions posted are welcome...

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