Diagnosis

Question

My daughter is 16 years and will have a sweat test done this week. Now I read that this is only an option in young children. Is this correct? Does it occur that the diagnosis of cystic fibrosis is only made during adolescence?

Answer

Dear Ecorn-user,

The sweat test is usually the first test done if one thinks of cystic fibrosis. The sweat test can be done from the age of 2 weeks on. In adolescents and young adults this test can thus be done without any problem.
Most of the time the sweat test will give a clear answer. A sweat chloride value above 60 mmol/l is diagnostic for cystic fibrosis. A sweat chloride value below 30 makes CF very unlikely. In between these 2 values there is a grey zone because the chloride value does not give a clear answer versus the possibility of cystic fibrosis. In this situation other diagnostic tests are needed such as extensively testing for CFTR mutations or direct measurements of chloride channel function in the nose (nasal PD test).
One can look at the data of a whole country and evaluate at what age the diagnosis of cystic fibrosis was made. Here are the data for Belgium: in half of the patients the diagnosis is made before the age of 1 year, even before the age of 6 months. In about 90% of the patients diagnosis is established before the age of 18 years, but in about 10% of the patients the diagnosis only becomes clear during adult life. These late diagnoses usually – but not always – concern milder forms of the disease.
Yours sincerely,
Prof. Kris de Boeck

26.01.2009