Sweat test result

Vraag

Hello,
today a sweat test has been performed to our 2 year-old son. The result has been 60 mmol/l sodium chloride.

The hospital informed us about the following interpretation:
80= pathologic

In all other publications however, other limits are mentioned:
60= pathologic

What is correct? Is there no uniform classification? We are going to do another test, but with this different classifications it seems not even possible to get a more meaningful result.....

Many thanks for your quick answer,
Yours sincerely,

Antwoord

Dear questioner,

First of all it is important to know how the sweat test had been performed in order to tell you the cut-off values. The correct method is based on a chemical measurement of the sweat.
According to current consensus statements there is a uniform classification: chloride values 60 mmol/l are considered to be consistent with the diagnosis of CF.
In case the result is >60mmol/l, a second test is recommended, if the result is again >60mmol/l this confirms the diagnosis of CF.
By time, we learned, however, that there are CF-patients with even lower or even a negative sweat-test result. Therefore, if the result is borderline (40-60mmol/l), the test should be repeated; if the result is still borderline, other measures to clarify the situation are done: e.g. a mutation analysis and if needed a measurement of the potential difference of the rectum mucosa, other diagnostic tools are the analysis of the function of the pancreas (stool-fat, the pancreatic enzyme elastase in the stool), microbiological investigation of the airways. In case the sweat test shows a negative result (under 40mmol/l) further diagnostic measures should be performed if the clinical symptoms still favour the diagnosis of CF.
Due to this quite complicated situation you shoud seek for advice at a CF-centre nearby. You can get addresses at the homepage of the German patient organisation (mukoviszidose e.V. Bonn).
I hope that I have helped you further with this information.
Yours sincerely,
Dr. H.-G. Posselt

23.04.2008