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What does not work !

Standard aggregation studies (particularly those using a PFA100) are NOT a reliable and sensitive method to test for Hermansky-Pudlak Syndrome.  Standard aggregometry should not be used as a first line screen for HPS.

Clear guidance has been issued in the UK regarding the use of standard aggregometry (in particular, the PFA100) to test for mild platelet bleeding disorders including HPS (Click here).  A number of reviews and research studies have also been published.  Results from this method often do not show the platelet defect of of HPS.  Such ‘false negative’ results may lead a doctor to exclude a diagnosis of HPS prematurely.  Other tests carried out using the same blood may confirm a diagnosis of HPS.

If standard aggregometry is carried out (including with the PFA100) then it should be backed up by either a nucleotide assay or electron microscopy.

Ask your haemotologist what approach they are going to use and ask them to use a combination of Methods.

Coagulation times

Standard laboratory tests for blood clotting (coagulation times) DO NOT identify the platelet defect of HPS. These include:

Coagulation times vary greatly from within normal range to outside normal range for those with HPS and so are not a reliable indicator for the platelet bleeding disorder of HPS.  More importantly the platelet defect of HPS is simply not measured by any of the above coagulation tests

However, the above tests of coagulation are carried out routinely within the UK National Health System (NHS) when a bleeding disorder is suspected.  This is an important safeguard because unrelated conditions can result in a pattern of bleeding symptoms similar to HPS.

Infact, approximately 30 percent of people who have HPS also have a decrease in both platelet and plasma von Willebrand's Factor (vWF) antigen activity.

Template bleeding time

This is also regarded as an unreliable indicator of for ‘mild’ bleeding disorders. This test involves making a small incision on the skin of the forearm and timing how long it takes for the blood to stop flowing from the cut.  The cut is typically made using a small spring loaded ‘punch that makes a incision of a specific length and depth.

For patients with HPS, template bleeding times vary from just outside normal range to highly prolonged. However, the bleeding time can be effected by several variables and can  vary over time for the same patient.  This is also the case for patients with a variety of bleeding disorders as well as for healthy people.

Bleeding history

Due to the wide variation in the bleeding tendency it is not sufficient to exclude a diagnosis of HPS due to an apparent lack of a clear history of bleeding - particularly in young children.  Experience has shown that for many people the first indication of a bleeding disorder was seen during surgery, dentistry, or trauma.

The hair bulb test

The hair bulb test should not be used as a screen to differentiate between people with a tyrosinase positive form of albinism, such as HPS, and those who have a tyrosinase negative form.

(Click here)

Remember !

It is possible for a person with albinism to have a bleeding disorder caused by a separate medical condition that is unrelated to either albinism or HPS.

It is also possible for someone with HPS to have a coagulation disorder in addition to that caused by HPS.

People who have either albinism or HPS are as prone to unrelated conditions and diseases as any other person.

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What else you need to know about testing for HPS