3 sweat tests – 3 different results, part II

Question

Dear Dr. Sommerburg,

I am submitting my question again, since it was not transmitted completely the first time.

My four-year-old son was admitted to the hospital with obstipation. Upon admission, his stool values were at 207 ug/g and the sweat test (sodium iontophoresis) at 30 mmol/l. Further tests during his stay – after purging measures with the help of Practo-Clyss®) – returned the following values: stool < 50ug/g; sodium iontophoresis 49 mmol/l. The head physician recommended further tests after two weeks. We had those done now, with the following results: stool at < 50 ug/g and sodium iontophoresis 38 mmol/l.

The head physician thinks all these values are within the normal range, except for the stool values. He suspects those to be only temporary, though, due to preceding infections, one asthma attack and stomach flu. He ascribes the differing sweat test values to my son’s condition on the days of testing.

Can I assume that everything is okay, or what should I do now? My pediatrician is trying to push me into the CF direction and urging me to take more tests. I would be grateful for a quick answer.

Kind regards

Answer

Hello,

Thank you for your submitting your question again. I can answer more precisely now.

Your son has repeatedly been tested for two different values, both of which were supposed to hint to a potential presence of cystic fibrosis. I would therefore like to start with the values for the pancreatic elastase in the stool. You currently have three different test results. One result is within the normal range, two are pathological. I think that, judging from these values, one cannot rule out exocrine pancreatic insufficiency, no matter if purging measures were taken or not. This means that it remains unclear whether your child has a pancreas problem the way it occurs in CF patients.

Regarding the sweat tests: unfortunately, different parameters are still being measured in the sweat today (chloride, sodium, conductivity, osmolarity), even though international guidelines settled on chloride measurement only already years ago. This was supposed to be the only parameter to be referred to for a definitive decision, particularly in unclear cases. If, however, your child has indeed been tested for sodium (and not for conductivity), then the head physician you are mentioning is wrong, since sodium values between 30 and 60 mmol/l are considered borderline values that do not at all allow for CF to be ruled out. Meanwhile, we know that there are several patients whose progression is not entirely classic and who can show such sweat test values.

Your pediatrician will have her reasons for thinking of CF and she would well advised to refer you and your child to a certified CF center. There you will find CF-competent doctors who will be able to recognize mild and atypical progressions of CF as well. Should there still be problems with the diagnosis, these certified CF clinics will refer unclear patients to so-called centers of reference, which offer the possibility of doing further tests (nasal potentials measurement, short-circuit current measurement in biopsies of the rectal mucosa). I am sorry, but I do not agree with the evaluation of the colleague you mention here, and I urge you to get further diagnostics done that should give you clarity one way or another!

Kind regards
Olaf Sommerburg

06.09.2010