Tuesday, 29 September 2015

What does the Transfusion Outcomes Research Collaborative's NAIT Registry do?

SPHPM's Associate Professor Erica Wood, Head of the Transfusion Research Unit, has been involved with the NAIT Registry since its inception in 2009. NAIT or FMAIT (neonatal or feto-maternal alloimmune thrombocytopenia) is a rare and serious condition that affects the platelet count. Special markers (also known as antigens) on the surface of platelets determine a person's platelet blood group. A baby inherits these markers from its mother and father, so in some cases a mother and baby can have different platelet groups. In this situation, the mother's immune defence system may perceive the baby's platelets to be "foreign". When this occurs, she may make antibodies, which can cross the placenta into the baby's blood and damage the baby's platelets, causing a low platelet count.

Associate Professor Wood  has overseen the collection of diagnosis, treatment and outcome data for 90 NAIT cases. The NAIT Registry represents the largest case series in Australia. There are currently 30 hospitals participating in the project, which is being run in conjunction with the Australian Red Cross Blood Service. Registry data has been presented at various conferences, including the International Society of Blood Transfusion in 2015, and there are plans to use data as a basis for a study of the long-term outcomes for babies affected by NAIT, when more cases have been accrued.

Eighteen-month-old Gray was born at Geelong Hospital with a platelet count of just 19  normal newborn platelet count is expected to be over 100. Gray needed three platelet transfusions and two doses of intravenous immunoglobulins (IVIg), to achieve a normal platelet count. After some time in the Special Care Nursery, he recovered well and is now a healthy and happy toddler.

Tests revealed that Gray's mother had developed antibodies to one of the paternally-inherited HPA molecules expressed on her baby's platelets. These antibodies had crossed the placenta and destroyed many of Gray's platelets, leaving him susceptible to bleeding, both during the pregnancy and after delivery.

Often in NAIT, small bleeds occur in the skin (petechiae) and sometimes there is bleeding from the mouth or nose, in the gut or lungs. However, the biggest concern in these foetuses and newborns is the risk of intracranial haemorrhage, which occurs in around 10 per cent of cases. This can be permanently disabling or even fatal.

There is no population screening for NAIT, so couples are usually unaware that they are at risk until complications are detected during an antenatal ultrasound, or when their baby is born with a very low platelet count. The good news is that, with treatment, most babies born with NAIT do very well. Any subsequent pregnancies for a couple can be managed with IVIg (a product extracted from donor plasma) to greatly reduce the risk to the baby, and the baby can be given IVIg and donor platelets shortly after birth if needed.

Clinical registries are very important in rare diseases such as NAIT, as a way of identifying variation in diagnosis and care and in inspiring and facilitating hypothesis-driven research, such as clinical trials.

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