Is the sweat test 100%

[rhrara]

2 of my daughters went this morning to have their sweat test done, and the doctor just called me and told me that both have abnormal levels. She said the norm is 0-50 and my 3 year old's level was 66 and my 5 year old's level was 80. Now she is sending us to the CF center down in Orlando, FL. Looking up all the information on this disease it has just devestated me, someone please help!

Robin

 

[rhrara]

2 of my daughters went this morning to have their sweat test done, and the doctor just called me and told me that both have abnormal levels. She said the norm is 0-50 and my 3 year old's level was 66 and my 5 year old's level was 80. Now she is sending us to the CF center down in Orlando, FL. Looking up all the information on this disease it has just devestated me, someone please help!

Robin

 

[rhrara]

2 of my daughters went this morning to have their sweat test done, and the doctor just called me and told me that both have abnormal levels. She said the norm is 0-50 and my 3 year old's level was 66 and my 5 year old's level was 80. Now she is sending us to the CF center down in Orlando, FL. Looking up all the information on this disease it has just devestated me, someone please help!

Robin

 

[Mommafirst]

I'm sorry you are going through this, Robin. But welcome, I'm sure you'll find amazingly supportive people here.<br>
<br>
The sweat test is certainly not 100% accurate, although from what I've read its much more likely to get a false negative than a false positive. Anyway, I don't know what your doctor is saying about the tests because I've always heard that 1-30 is normal, 30-60 (sometimes 40 on the low end) is borderline, and anything over 60 is positive. Of course all that goes out the window if your kids were not tested at an accredited CF center. There are many parents on this board with kiddos whose sweats were borderline or even high normal, so the sweat test is NOT definitive. I'd highly suggest you insist that they run genetic testing so you can know more concretely. <br>
<br>
I know its overwhelming and incredibly upsetting to be facing diagnosis. But your girls are the same girls they were before. I don't know what kinds of symptoms prompted the testing, but the good news is if you get a diagnosis you can help them. There are lots of good treatments that can help them absorb food and nutrients, and keep their lungs healthy for as long as possible! <br>
<br>
Keep us posted, and best of luck.

 

[Mommafirst]

I'm sorry you are going through this, Robin. But welcome, I'm sure you'll find amazingly supportive people here.<br>
<br>
The sweat test is certainly not 100% accurate, although from what I've read its much more likely to get a false negative than a false positive. Anyway, I don't know what your doctor is saying about the tests because I've always heard that 1-30 is normal, 30-60 (sometimes 40 on the low end) is borderline, and anything over 60 is positive. Of course all that goes out the window if your kids were not tested at an accredited CF center. There are many parents on this board with kiddos whose sweats were borderline or even high normal, so the sweat test is NOT definitive. I'd highly suggest you insist that they run genetic testing so you can know more concretely. <br>
<br>
I know its overwhelming and incredibly upsetting to be facing diagnosis. But your girls are the same girls they were before. I don't know what kinds of symptoms prompted the testing, but the good news is if you get a diagnosis you can help them. There are lots of good treatments that can help them absorb food and nutrients, and keep their lungs healthy for as long as possible! <br>
<br>
Keep us posted, and best of luck.

 

[Mommafirst]

I'm sorry you are going through this, Robin. But welcome, I'm sure you'll find amazingly supportive people here.<br>
<br>
The sweat test is certainly not 100% accurate, although from what I've read its much more likely to get a false negative than a false positive. Anyway, I don't know what your doctor is saying about the tests because I've always heard that 1-30 is normal, 30-60 (sometimes 40 on the low end) is borderline, and anything over 60 is positive. Of course all that goes out the window if your kids were not tested at an accredited CF center. There are many parents on this board with kiddos whose sweats were borderline or even high normal, so the sweat test is NOT definitive. I'd highly suggest you insist that they run genetic testing so you can know more concretely. <br>
<br>
I know its overwhelming and incredibly upsetting to be facing diagnosis. But your girls are the same girls they were before. I don't know what kinds of symptoms prompted the testing, but the good news is if you get a diagnosis you can help them. There are lots of good treatments that can help them absorb food and nutrients, and keep their lungs healthy for as long as possible! <br>
<br>
Keep us posted, and best of luck.

 

[rhrara]

Thank you, I appreciate it greatly. We had the test done at Halifax Hospital which is one of the best hospitals in our area. I will post what happens when I get more information.

Robin

 

[rhrara]

Thank you, I appreciate it greatly. We had the test done at Halifax Hospital which is one of the best hospitals in our area. I will post what happens when I get more information.

Robin

 

[rhrara]

Thank you, I appreciate it greatly. We had the test done at Halifax Hospital which is one of the best hospitals in our area. I will post what happens when I get more information.

Robin

 

[okok]

Hi

It sounds like your doctor is doing the right thing in suggesting that your childern go to a CF center for further testing. i think the rate of false positives is slightly more common then false negatives. When a sweat test is preformed properly the false negative rate is something like 12% and the false positive rate is 15%, if i remember properly.

False positves can be caused by the use of steriods or certain medications and some conditions other than cf can sometimes cause higher sweat chloride values.

I think that false negatives most commonly occur when the sweat rate is too slow....in which case they should not preform the sweat test. (This falls in the catagory of improperly preformed sweat tests.) Sometimes an inexperienced technician may continue to collect sweat past the normal collection time frame in order to ensure they get "enough" sweat. This means that the sweat rate is too slow which can cause the sweat chloride to appear to be lower than it really is. False negatives are also caused by protien malnutriton when there is swelling at the site of sweat collection. Some cfers just have lower sweat chloride values though.

You could ask your doc how the sodium compared to the chloride. Cfers tend to have an elevated choride to sodium ratio compared to people without CF (ie cfers have more chloride than sodium in their sweat).

best of luck! i hope the additional testing is negative! please let us know how it goes for you and your family. You will probably want to get genetic testing done if their continues to be ambiguity in your childern's sweat choride levels.

 

[okok]

Hi

It sounds like your doctor is doing the right thing in suggesting that your childern go to a CF center for further testing. i think the rate of false positives is slightly more common then false negatives. When a sweat test is preformed properly the false negative rate is something like 12% and the false positive rate is 15%, if i remember properly.

False positves can be caused by the use of steriods or certain medications and some conditions other than cf can sometimes cause higher sweat chloride values.

I think that false negatives most commonly occur when the sweat rate is too slow....in which case they should not preform the sweat test. (This falls in the catagory of improperly preformed sweat tests.) Sometimes an inexperienced technician may continue to collect sweat past the normal collection time frame in order to ensure they get "enough" sweat. This means that the sweat rate is too slow which can cause the sweat chloride to appear to be lower than it really is. False negatives are also caused by protien malnutriton when there is swelling at the site of sweat collection. Some cfers just have lower sweat chloride values though.

You could ask your doc how the sodium compared to the chloride. Cfers tend to have an elevated choride to sodium ratio compared to people without CF (ie cfers have more chloride than sodium in their sweat).

best of luck! i hope the additional testing is negative! please let us know how it goes for you and your family. You will probably want to get genetic testing done if their continues to be ambiguity in your childern's sweat choride levels.

 

[okok]

Hi

It sounds like your doctor is doing the right thing in suggesting that your childern go to a CF center for further testing. i think the rate of false positives is slightly more common then false negatives. When a sweat test is preformed properly the false negative rate is something like 12% and the false positive rate is 15%, if i remember properly.

False positves can be caused by the use of steriods or certain medications and some conditions other than cf can sometimes cause higher sweat chloride values.

I think that false negatives most commonly occur when the sweat rate is too slow....in which case they should not preform the sweat test. (This falls in the catagory of improperly preformed sweat tests.) Sometimes an inexperienced technician may continue to collect sweat past the normal collection time frame in order to ensure they get "enough" sweat. This means that the sweat rate is too slow which can cause the sweat chloride to appear to be lower than it really is. False negatives are also caused by protien malnutriton when there is swelling at the site of sweat collection. Some cfers just have lower sweat chloride values though.

You could ask your doc how the sodium compared to the chloride. Cfers tend to have an elevated choride to sodium ratio compared to people without CF (ie cfers have more chloride than sodium in their sweat).

best of luck! i hope the additional testing is negative! please let us know how it goes for you and your family. You will probably want to get genetic testing done if their continues to be ambiguity in your childern's sweat choride levels.

 

[Justsmurfin]

Actually steroids cause false negative NOT false positive results

Heres a good link talking about false negative/false positive tests and the sweat test in general

<a target=_blank class=ftalternatingbarlinklarge href="http://www3.nbnet.nb.ca/normap/sweattests.htm
">http://www3.nbnet.nb.ca/normap/sweattests.htm
</a>
For the record we were told false positives are rare if the test is done correctly. False negatives are much more common both when the test is done correctly and incorrectly

 

[Justsmurfin]

Actually steroids cause false negative NOT false positive results

Heres a good link talking about false negative/false positive tests and the sweat test in general

<a target=_blank class=ftalternatingbarlinklarge href="http://www3.nbnet.nb.ca/normap/sweattests.htm
">http://www3.nbnet.nb.ca/normap/sweattests.htm
</a>
For the record we were told false positives are rare if the test is done correctly. False negatives are much more common both when the test is done correctly and incorrectly

 

[Justsmurfin]

Actually steroids cause false negative NOT false positive results

Heres a good link talking about false negative/false positive tests and the sweat test in general

<a target=_blank class=ftalternatingbarlinklarge href="http://www3.nbnet.nb.ca/normap/sweattests.htm
">http://www3.nbnet.nb.ca/normap/sweattests.htm
</a>
For the record we were told false positives are rare if the test is done correctly. False negatives are much more common both when the test is done correctly and incorrectly

 

[okok]

hey rebekah,

thanks for clarifying that about the steroids. i went and double checked all my info since i was so mixed up. I can email pdf's of the articles where i am getting this info if you pm me.

published in thoracic march 1 2005

"The incidence of erroneous sweat test results is probably in the range of 10-15%, and most errors represent false-positive results. Most errors are caused by the use of unreliable methodology, inadequate sweat collection, technical mistakes, and misinterpretation of results; therefore, the test should be performed in a laboratory that regularly uses extreme care with assays. False-negative results can be seen in hypoproteinemic edema and with the concurrent administration of steroids."

I'm guessing that false negative refers to a sweat chloride result which is NOT representative of the individual's actual physiological sweat chloride levels. if you were to consider the individuals with cf who physiologically have sweat chloride levels in the normal or borderline range as false negatives then the proportion of false negatives would probably be greater. Apparently 23% of people with sweat chloride between 30-60 mM have 2 CFTR mutations.

About the ratio of chloride/sodium:

About 75% of people with CF have a chloride/sodium ratio of greater than 1. This means about 25% of people with CF will still have a chloride to sodium ratio of less than 1. I would say that if your childern have a ratio less than 1 you should definately still have further testing (genetic and sweat testing) but that it is ok to feel hopeful that the sweat tests values might be falsely positive. Of course, I'm saying this without knowing anything about your childern's symptoms.

Again best of luck to you. Let me know if you would like me to pm you the articles containing this info.

 

[okok]

hey rebekah,

thanks for clarifying that about the steroids. i went and double checked all my info since i was so mixed up. I can email pdf's of the articles where i am getting this info if you pm me.

published in thoracic march 1 2005

"The incidence of erroneous sweat test results is probably in the range of 10-15%, and most errors represent false-positive results. Most errors are caused by the use of unreliable methodology, inadequate sweat collection, technical mistakes, and misinterpretation of results; therefore, the test should be performed in a laboratory that regularly uses extreme care with assays. False-negative results can be seen in hypoproteinemic edema and with the concurrent administration of steroids."

I'm guessing that false negative refers to a sweat chloride result which is NOT representative of the individual's actual physiological sweat chloride levels. if you were to consider the individuals with cf who physiologically have sweat chloride levels in the normal or borderline range as false negatives then the proportion of false negatives would probably be greater. Apparently 23% of people with sweat chloride between 30-60 mM have 2 CFTR mutations.

About the ratio of chloride/sodium:

About 75% of people with CF have a chloride/sodium ratio of greater than 1. This means about 25% of people with CF will still have a chloride to sodium ratio of less than 1. I would say that if your childern have a ratio less than 1 you should definately still have further testing (genetic and sweat testing) but that it is ok to feel hopeful that the sweat tests values might be falsely positive. Of course, I'm saying this without knowing anything about your childern's symptoms.

Again best of luck to you. Let me know if you would like me to pm you the articles containing this info.

 

[okok]

hey rebekah,

thanks for clarifying that about the steroids. i went and double checked all my info since i was so mixed up. I can email pdf's of the articles where i am getting this info if you pm me.

published in thoracic march 1 2005

"The incidence of erroneous sweat test results is probably in the range of 10-15%, and most errors represent false-positive results. Most errors are caused by the use of unreliable methodology, inadequate sweat collection, technical mistakes, and misinterpretation of results; therefore, the test should be performed in a laboratory that regularly uses extreme care with assays. False-negative results can be seen in hypoproteinemic edema and with the concurrent administration of steroids."

I'm guessing that false negative refers to a sweat chloride result which is NOT representative of the individual's actual physiological sweat chloride levels. if you were to consider the individuals with cf who physiologically have sweat chloride levels in the normal or borderline range as false negatives then the proportion of false negatives would probably be greater. Apparently 23% of people with sweat chloride between 30-60 mM have 2 CFTR mutations.

About the ratio of chloride/sodium:

About 75% of people with CF have a chloride/sodium ratio of greater than 1. This means about 25% of people with CF will still have a chloride to sodium ratio of less than 1. I would say that if your childern have a ratio less than 1 you should definately still have further testing (genetic and sweat testing) but that it is ok to feel hopeful that the sweat tests values might be falsely positive. Of course, I'm saying this without knowing anything about your childern's symptoms.

Again best of luck to you. Let me know if you would like me to pm you the articles containing this info.