Sweat Chloride

[anonymous]

I have recently taken my daughter for a sweat chloride test. Her result was 49. I have researched every website possible for this test. I had the test taken at a local hospital and I have since been advised by someone on this forum (advice that I am taking) to get the test taken at a CF care center. Here is my question. My peditrician believes that my daughter is fine. I tend to agree as she has very few CF type symptoms. But one reason he feels so confident is the lab that did the sweat chloride showed the result ranges to be as follows:
0 - 60 noral
60 - 80 equivocal
> 80 diagnostic CF

As I mentioned, I have done so much research but yet I can not find one single site that has 0 - 60 as normal. All sites I have found have 0 -40 as normal , 40 - 60 equivocal and > 60 diagnostic CF. If there is such a test, what is the difference in it and the sweat chloride. Is 49 anything to be worried about with either test.

By the way, I have her scheduled at Egleston Hospital in Atlanta on Tuesday.

May God bless you.
ji

 

[BaylorCrew07]

I have never heard the scale that your doctor is talking about, I've always been told the one that you have found in research (0-40 normal, 40-60 inconclusive, 60+ CF) I was actually diagnosed with a sweat test of 62 a few months ago, then genetic testing confirmed that i do have cf.

As you have already decided to do, getting her tested at a CF clinic is the best thing to do. I was pretty asymptomatic until recently and I had many sweat tests as an infant all coming back in between 40 and 50, but I have a 'milder gene mutation' apparently.

I don't tell you that to get you worried, but just to confirm that you have made the right decision <img src="i/expressions/face-icon-small-smile.gif" border="0"> if her sweat test is still between 40 and 60 it would also be good to get a genetic test, because they can detect over 1000 mutations, while a inconclusive sweat test can't really tell you much.

I hope everything goes well, good luck!

Debra

 

[anonymous]

I think it depends on what they're testing. The "gold standard" for the sweat chloride test is 0-40; 40-60; >60, as your research shows. However, there are some labs who do not follow the CFF's recommended method of testing. Instead they test the chloride level instead of the sodium level (I think that's right). THose ranges are different. Again though, these labs are NOT using the CFF's (Cystic Fibrosis Foundation) accepted testing protocal. I'll look to see if I can find a link detailing the difference. At any rate, I think you are best to do what you are doing - follow up with a sweat chloride test at a CFF accredited hospital.

 

[anonymous]

Ok, well this talks a little bit about the chloride versus sodium content. Also, apparently, I had it backwards. The standard scale they use (0-40 -, 40-60 B, >60 +) refers to the CHLORIDE concentration. Here's an excerpt from <a target=new class=ftalternatingbarlinklarge href="http://www.cysticfibrosismedicine.com/htmldocs/CFText/sweat.htm
">http://www.cysticfibrosismedicine.com/htmldocs/CFText/sweat.htm
</a>
When analyzing a sweat test the chloride concentration shows greater discrimination than sodium (Green et al, 1985; Hall et al, 1990; Gleeson et al, 1991, Kirk et al, 1992, Shwachman et al, 1981). A chloride value of >60 mmol/l is considered positive, between 40 and 60 mmol/l equivocal and less than 40 mmol/l negative. A chloride sweat concentration of 40-60 mmol/l in infancy is suspicious of CF (Massie et al,2000). Sodium concentrations should not be interpreted without a chloride result. A sodium value of less than 60 mmol/l is unlikely to be associated with cystic fibrosis (not in atypical CF). Values above 90 mmol/l support the diagnosis. A chloride concentration which is less than the sodium concentration or a discrepancy between the two of > 20 mmol should be regarded with suspicion.

From this excerpt, it sounds like your pediatrician is looking at the SODIUM value instead of the CHLORIDE value which is the gold standard. I'd say either your pedi doesn't know how to read the report or your lab did a poor job reporting (which probably means they're not accredited.)

Good luck with your next sweat test.

 

[anonymous]

That does clear some things up. I will call them and get them to fax me the results so I will know the type of test they ran. The hospital I went to is certainly not a CF care center so I will bypass their results all together. I have serious questions why they would elect to do the sodium concentration versus the sweat chloride.

Thank you both.

 

[anonymous]

New study on sodium concentration:

<a target=new class=ftalternatingbarlinklarge href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15689903&dopt=Citation
">http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15689903&dopt=Citation
</a>