When we or our physician suspect Prader-Willi Syndrome (PWS) the next step is a blood test.
In lot’s of countries of the World where PWS awareness is not so strong there is a big confusion and mistake what physicians make:
“they are sending the parents with their kids only to check the FISH method of testing and with this they do not rule out PWS 100%!After getting the negative FISH test result, the parents calm down and get reassured that their child does not have PWS.
But! nobody knows that with the FISH analysis they only ruled out PWS 50%!”
And meantime PWS takes it’s price :
NO Growth Hormone Therapy!
NO food control,
…and practically the child is in a life threatening condition!
Parents and physicians start to suspect PWS again when it is already too late!
This is a very common and dangerous mistake and the same happened with us when we wanted to diagnose Stony at age 2. Thanks to IPWSO and to the fact we speak english we did not give up and made our research..so Stony finally was diagnosed at age 2,5.
In countries where the technology is not so advanced and/or methylation test is still not available or expensive the physician send the child with the suspected Prader-Willi Syndrome to test it with the FISH analysis. FISH analysis identifies only one genetic subtype of PWS called: deletion. Deletion occurs in only 50% of PWS cases. The other 50% of PWS cases are due to the other subtype called: uniparental disomy (UPD) what can be only detected with the method of testing called: methylation analysis.
Methylation analysis detects >99% of cases including all of the major genetic subtypes of PWS. (deletion, uniparental disomy, or imprinting mutation (2%))
It is extremely important to be aware of this information and when we are getting our laboratory test referral we should consult with the physician about these crucial details.
It can be an option first to make the FISH analysis and see what result it brings but if this this results negative is definitely needed to keep going and follow with the Methylation test in order to rule out PWS >99%.
Almost all cases of PWS can be confirmed by one of the above test, however in the rare event that laboratory tests do not confirm PWS a clinical diagnosis can be helpful and crucial for the development of a management plan.