Bit confused about Elastase vs sweat test

[Kelly87]

Would someone please help me with this doubt...

With my 3-year-old son, I ended up at the pediatrician because of his low weight (13kg/99cm).

There I expressed my concern about the possibility of CF, because of some symptoms (meconium only after 48 hours after enema, somewhat longer jaundice after birth, often coughs for periods after colds, bulky, fatty stools that float and of course the weight which is lagging behind).

The doctor did not fully agree with my idea about this, but I insisted on having elastase tested and a sweat test.

Elastase was 405 and the sweat test negative (15cl / 18na).

Only ... now I know that elastase is usually >500 and that sweat tests can sometimes be false negative. My doctor, however, called me with the message that CF is now 100% excluded.

I have a hard time letting this go because of the symptoms. I notice that DNA testing is being used with caution. Am I entitled to this in view of the doubts I otherwise hold?

How do you read the results of the 2 tests in relation to the symptoms?

 

[Ratatosk]

Do they do newborn screening in your area? DS was born with meconium ileus and required bowel surgery when he was a day old. Because of his symptoms, a doctor at the local hospital requested a basic genetic screen -- 99 of the most common mutations from Mayo. When he had his sweat test at 3 weeks it was 37 with normal being 39 or less. I just found his lab results on the hospital website and I recall the cf doctor saying "I don't know why they bothered doing an elastase test as we know from his symptoms, surgery that he's pancreatic insufficient. So they never gave us the results at the time.

Results of his elastase showed Severe exocrine pancreatic insufficiency with a 2.8 from a test of

> 200 mcg E/g stool

Not all people with cf are pancreatic insufficient, and sometimes it's difficult to get a good sample for the sweat test. The CFF recommends a sweat test at an accredited facility. In our case, DS' eventually proved to be very salty. Sweats out an enormous amount of salt in the summer to the extent his hats are white with salt.

Your child is older, my child was tested in the NICU when he was only a couple weeks old. It could be that he's just tiny. Because he is having issues, I would ask

"if not CF, then what". ​

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[Kelly87]

Thank you Ratatosk,

He passed the newborn screening, but that "could be" because he seems to be Pancreas sufficient according to the recent test result at least.
The confusing part is that they never called it 'Meconium Ileus' nor did he need surgery. It was solved through the use of an enema, but they also didn't perform an ultrasound so no idea what exactly caused the blockage. Wondering if that could be something benign and unrelated...

They did get enough sweat for the sweat test and the numbers are quit low... it's just that meconium thing and the symptoms that all point to CF.... keeps me worried

 

[Ratatosk]

Hopefully you can get some answers. We had so many confusing test results at first --- not a large enough sample obtained for both blood and sweat tests, then the normal sweat test, so despite DS' obvious symptoms, there were always questions in the back of my mind.

Would be nice if they could figure out his issues.