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Relevance of the sweat test
- Question
- My grandson, 4 years old, has problems with his intestines and airways since birth. He had a sweat test and the value was 45. After that no further examination was done because he did not have any further complaints. Now he however again is short of breath and has abdominal pain. Is it, given the value of 45, better to do further tests?
- Answer
- As you know, Ecorn is not a medium where we give advice about specific medical situations. We just provide answers to general questions related to CF.
The cut off values for normal and abnormal sweat test depend on which test is used. In case of a conductivity test, it is higher than in case of the classical Gibson & Cook test. In addition it is unclear whether you discuss the values for chloride or for sodium. Also the test needs to be done by a person with sufficient experience and a sufficient amount of sweat needs to be collected. So whether the result that you mention is from a valid test and whether it is normal or abnormal can thus not be stated with certainly. If a patient has symptoms that are suggestive for CF it may be indicated to repeat a sweat test.
Such a test should be performed in an experienced CF center and it should measure the chloride concentration in the sweat by a so-called "pilocarpine ionotophoresis" as this is the gold-standard and conductivity measurement is not appropriate.
In the case of your grandson we suggest that the parents discuss his situation with his doctor.
We hope that this answer helps you.
Prof. Kris de Boeck
- 14.05.2012
