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Sweat Test Result

Question
I have read data regarding the sweat test for CF and at an approved centre I believe a result over 60 confirms the diagnosis of CF. Can you tell me please if the higher the figure has any relation to the effect of the disease? For example if the sweat test results with a child over 8 months was in the 80's and another child's result was 100+ does this mean anything specific other than there has been a definite diagnosis? Thank you for reading and hopefully answering this.
Answer
Dear Questioner
Many thanks for your question. You are correct in saying that a sweat chloride result of 60 mmol/L does represent an abnormal result.

There may be an association between the sweat chloride result and the severity of disease. One study (Wilschanski et al 2006) has shown that patients who have pancreatic sufficiency (i.e. do not have to take enzymes; typically less severe disease) have on average a lower sweat chloride than patients with pancreatic insufficiency (i.e. do have to take enzymes; typically more severe disease).

It is extremely difficult however to predict disease severity for an individual, especially when that individual is very young. Your CF doctor would be able to give you more specific advice.

Best wishes
Lisa Kent
Damian Downey

Reference:
Wilschanski et al. Mutations in the Cystic Fibrosis Transmembrane Regulator Gene and In Vivo Transepithelial Potentials. American Journal of Respiratory and Critical Care Medicine 2006; Volume 174: pages 787-794.
20.07.2012
The answer is edited by: PhD Lisa Kent