sweat test vs. blood

[anonymous]

We've got a family history of cf, my wife's a carrier and we'll be having a baby in the next couple months. Even if there are no symptoms, we'd like to test for cf for peace of mind.

I've searched the internet and this site for the answer, but with no luck . . .

In what cases are a sweat test more appropriate/accurate vs a blood test or cheek swab for DNA/genotype? If we decide on a blood test it sounds like Ambry or Qwest test for the most mutations?

Thank you so much!

 

[JazzysMom]

Since you have a family history of CF I would suggest the blood test. Besides determining if the child has CF itself, you can find out if they are a carrier & if so what mutation of the gene they have. If the baby had a sweat test that would only be for the diagnoses of CF itself & has nothing to do with being a carrier. My understanding is to use QUEST since they test for a larger number of mutations, but obviously that depends on any insurance involved.

 

[1princess]

We found out during this pregnancy that my husband and I are both carriers so we are planning on having our baby's cord blood tested when she is born. You can talk with your pediatrician and they can tell you specifically what your OBGYN will need to do (basically put it in the right color test tube or something for the genetic testing).

I have been monitored throughout my pregnancy with Level 2 ultrasounds looking for anything abnormal in the bowels (meconium illius) - this was done basically because many babies born with this need surgery right away and if we were going to have this problem I needed to deliver at a different hospital - everything looks fine for us, but we will have our daughter tested as soon as she is born!

Good luck getting the answers you need and best wishes for a healthy baby!

 

[anonymous]

They can also test with an amnio, not sure how much more or less accurate this is than a blood test though.

 

[anonymous]

Personally, I would just use Ambry to start with - and I would start by having your blood tested (now) to see if you are a carrier. If you get a negative from Ambry and the baby starts to show any symptoms then you should consider doing a sweat test (once that baby is at least a few weeks old) and a blood test with Quest - for the baby. The test with Quest is MUCH MUCH MUCH more expensive (like $2,000 more than Ambry) and your insurance may not even approve it as a starting point. Since you know that your wife is a carrier, she must carry one of the more common mutations (that tests like Ambry or Genzyme can detect).

My daughter (2.5 wCF) has a rare mutation that Ambry cannot detect with its scan but Quest was able to locate it (they look at the entire CFTR protein for all mutations rather than just scan for the more common mutations) then we went through an amnio to find out if the baby I am pregnant with now has CF. The amnio is just as accurate as the blood test (they both grow tissue culture in basically the same way).

Best of Luck to you!

 

[julie]

Word is coming out of the woodwork about the credability of AMBRY's test, and admittadely I once endorsed them. Here is a link to a previous topic I posted..... <a target=new class=ftalternatingbarlinklarge href="http://forums.cysticfibrosis.com/messageview.cfm?catid=5&threadid=4194&FTVAR_MSGDBTABLE=">http://forums.cysticfibrosis.com/messageview.cfm?catid=5&threadid=4194&FTVAR_MSGDBTABLE=</a>. Most insurance companies are more likely to cover Quest, they are a reputable and popular company and have been around for decades. The same can't be said for Ambry. Not that Ambry is bad, but, well, you'll see if you visit the other post and if you visit the sites.

You said your wife is a carrier, is the history of CF on just her side or yours as well? Personally, I would opt for the blood test, but on you if you are looking for answers right now. Otherwise, you can wait until the baby is born and test the baby at that time. Sometimes people can't wait, I don't think I could.

As far as your question about blood test versus sweat test, it's a complicated question with no true answer. Many CFers have had repeated negative sweat tests, only to be blood tested and found to have CF because of the 2 CF mutations. Other CFers have had positive sweat tests but the blood tests (the advanced test like from Quest) can only find one mutation. Other CFers have had a positive sweat tests but no mutations or only one mutation show up on a limited blood panel, and then go on to have their blood tested by quest and they find one or both of the mutations. Sweat tests are also somewhat inaccurate on infants up to a certain age (not sure what age, parents help me out here....). I would say it boils down to the knowledge of the doctor or CF center you will take your infant to for testing, your insurance coverage (will they cover a sweat test and then a blood test just to "be sure") and how much you might have to pay out of pocket if the sweat test shows nothing or borderline but you want a blood test and insurance won't pay.... these things might limit your choices.

Either way, best of luck and please do let us know the results whichever route you choose.

 

[anonymous]

DD was born with a bowel obstruction because of meconium illeus. No family history of CF and we looked way way back in our family trees. Sweattest came back normal -- not borderline, not inconclusive but a very low normal number; however, a suspcious doctor had some blood drawn and sent to Mayo. And another doctor at the hospital had ordered one too. Both came back with double deltaf508. So normal sweat test. Blood test = CF.

 

[anonymous]

I would do both actually. I would start with a less expensive DNA test like Genzyme and depending on those results and sweat test results go for Quest DNA testing. Quest has been the most highly reccomended to me.

Most states do newborn testing for CF don't they? So if you are the US its likely that will be done. I imagine that can miss some cases as well but combined with everything else give you a good answer

 

[anonymous]

(original poster)

Thank you each for your input! We are looking forward to a visit with our pediatritian with more info and questions. Will also look into what tests/labs our insurance will cover. Thanks again.