The Vice President of the HPS Network, Heather Kirkwood, is a friend of mine. 
She lives here in my area and did the bowl-a-thon with us the last 2 years. She gave me some more information about the blood test for HPS.
Testing for HPS is not yet a genetics-based test
because we are certian that not all of the genes that can cause HPS
have been found. As a result, gene testing could lead to a false
negative. Also, commercial testing for HPS is only available for the
Puerto Rican mutations of the HPS 1 and HPS 3 genes at this time - all
other gene testing is done as part of a research protocol.
Because they can't test genetically in a conclusive way
yet, they use a test that involves looking at the blood platelets under
an electron microscope. This is a very fancy type of microscope and the
average hospital lab doesn't typically have one. Dr. White at the
University of Minnesota invented the test and has the most experience
of anyone in the world at looking at blood platelets to diagnose HPS.
He looks at the membranes of the cells to see if he can find dense
bodies. These are little sacs of chemicals that burst open when you're
bleeding and help your blood platelets stick together to form a clot.
People with HPS do not have these dense bodies, and thus, if Dr. White
can't find them, the HPS diagnosis is made.
It is common for doctors to want to diagose HPS using
a bleeding time test. This is not an accurate way to diagnose HPS.
While many people with HPS do have longer bleeding times, not all do.
PT/PTT tests are common to look for bleeding disorders, but these tests
will come back normal for someone with HPS. This is why we advocate for
people with albinism being tested. If someone is in a trauma and is
unaware that they have HPS (because they haven't been a severe bleeder)
and suddenly there's a problem, the docs. will do these other tests and
they'll come back normal. They won't understand how to treat the
problem in an emergency.
If anyone is interested in arranging testing for HPS,
Dr. White has a grant to perform the test for free. The cost involved
to the patient involves getting the blood drawn and shipment of the
blood.
If you'd like to be tested, it's a good idea to
contact the HPS Network. The Network can discuss your medical history
with you, explain to you or your doctor how to take the blood and send
it to Dr. James White and set provide support both during the testing process
as well as afterwards.
The
HPS Network Inc.
1 (800) 456-9477 / 516.922.4022
Mashawna
http://www.parentofachildwithalbinism.com
