Pre-Natal Testing UPDATE!

[Guest guest]

As promised, here's an update on pre-natal testing from Amar Kamath

at Athena. First is his explanation, below that are my questions.

~ Gretchen

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Gretchen:

The 80% sensitivity is not for each assay, but as a hole for all CMT

tests that Athena offers. Let me explain it this way - if there were

a 100 patients with CMT and all of them had the complete CMT test, we

would find mutations in approximately 80 of them. This is called the

clinical sensitivity.

There is something called the technical sensitivity. This is where

you ask if there were a 100 patients with mutations in the PMP22

gene, how many would be identified with a PMP22 test? With our test,

the answer is >99%, in other words, we would find all of them. This

speaks to the technology we use for mutation detection.

In terms of our CMT1A test, we use a technology called " MLPA " - not

the FISH test. The problem with the FISH test is that it is

qualitative and depends on the skill-level of the person doing the

analysis, and we have had several cases where the FISH test was

negative (done at another lab), but we were able to identify the

mutation.

Prenatal testing can be done using one of two technologies - FISH or

MLPA. Athena uses MLPA. There are labs that use FISH, and they are

quite good at it, so I can't say don't use them. I would just say -

make sure the lab technician doing the analysis has a lot of

experience.

Other than CMT1A, we can routinely test CMTX prenatally, but if our

lab directors approve, we can test for any gene prenatally.

Hope this helps.

Amar

Hello Amar,

Me again. Another question: how reliable is the CMT 1A pre-natal

test - the one that can test the baby in utero? I think it is the

FISH test? Does that test carry the same 80% rate as the other DNA

CMT tests do? How long has this pre-natal CMT 1A test been around?

Also, can you please let me know an update on other types that can be

tested for pre-natally? Thanks.

Gretchen at

[Guest guest]

Anecdotally - I recently had this done through a chorionic villius sampling

(CVS) at 11 weeks gestation, and Athena tested the sample. CVS can only be done

between 10-12 weeks gestation. After your doctor removes the sample, it has to

grow in their lab for a couple of weeks. Then, they send it to Athena, which

takes a couple more weeks.

Athena was initially unable to determine whether the CVS sample (i.e., the baby)

had CMT1A (as I do) because of the DNA markers they test, all were identical to

mine and statistically, they expect at least 1 to be different. This means the

sample had CMT1A, but they couldn't tell whether the sample was the baby's or

mine. They sent it to another lab (I believe Boston University) that could test

for more DNA markers, and discovered that yes the sample was the baby's, and

therefore he has CMT1A.

To have our answer, the process took much longer than we anticipated - like

18/19 weeks gestation. It was a nerve wracking process, but I am very glad we

did it.

[Guest guest]

So...depends on the technician then? The Houston lab used FISH. I doubt there

are any false positives with it but perhaps something could be missed.

Thanks for getting this info, Gretchen