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Right performance of the sweat test?

Last week a sweat test had been done to our daughter Lara (16 months), because she has had two times a severe bronchitis within 3 months, where she could not cough up the mucus.
We have been informed about the result of 51, which does not really calm us after all we have read about it. Furthermore, we are not sure, if the test had been performed in the correct way.
In Lara's case sweat had been collected on the back. However at the first attempt, both collection reservoirs leaked out after 20 minutes, so that there was not enough material left to do the test. Therefore we repeated the whole procedure right away, but this time Lara was not wrapped up as thick as before and should not run along the hallway as long as before. After 10-15 minutes the nurse controlled the reservoirs and said that now the amount was suitable for the test.
In all publications however, it is mentioned that the period of collecting the sweat should be 30 minutes....
Can a lower deviation of time influence the result? And is it allowed to repeat the test right away if the first attempt did not bring out the needed material for the test? Would it be advisable to repeat the test at a CF-centre?

Many thanks for your answer in advance!
Yours sincerely,
Dear questioner,
Your question whether the sweat test should be repeated at a CF-centre is easy to answer. The sweat test brings only reliable results, where many tests per year are performed preferably by the same person. This is mostly the case at a CF-centre.
To the sweat test itself: international guidelines exist for the correct performance of the sweat test: The choice of the area of the skin is important (e.g. no atopic eczema, injuries etc), furthermore the sweat should be collected only at the arms and legs. The duration of the collecting period is also very important, the sweat should be collected for exactly 30 minutes, to fall below or to exceed this time period can lead to false results. Furthermore, the duration and intensity of provocation of secretion of the sweat is important; the standard method is the stimulation by pilocarpine (pilocarpine ionotophoresis). The chloride and sodium concentrations as well as the amout of sweat should be part of the sweat test result.
In conclusion, your description of the performance of the sweat test to your daughter sounds as if some major points considering the international guidelines have not been respected. It would be helpful for sure (apart from redoing the test at a CF-center) to get in dialogue with the hospital again in order to improve the performance of the sweat test there.

Yours sincerely,
Dr. M. Ballmann