Elastase, CF and diagnostics

Question

My 2 years old daughter is being examined for cystic fibrosis because she is growing poorly since the age of 8 months. There are no other complaints, but I had noticed before that her skin was tasting rather salty. They found 1 mutation, delta F508. For the other mutation sequence analysis are being done but we have to wait for months to get the result. The sweat test was done 3 times, it failed 2 times and once was a dubious result with rate 49 on the conductance measurement, elastase was fine 490. I wonder if she can have poor growth if the elastase is normal. De pediatrician said to us that it didn’t look good, but after the result of the elastase she said that it wasn’t certain that our daughter was suffering from CF. At this point we are rather confused. How should we think about the elastase and the poor growth? Our daughter is allergic for dairy and egg. Could she have CF but the poor growth not because of CF but because of the allergy? Or has some diagnosis been missed and is poor growth despite the good elastase secondary to CF?

Answer

Dear Ecorn-user,
We understand your concern about your daughter. We however need to point out that the aim of the ECORN project is not consultation for unsolved individual problems. Rather It is an information platform for general questions about CF.
About the diagnosis of CF we can state the following. In most patients it is easy to confirm the diagnosis because of obvious symptoms and a clearly abnormal sweat test result. In a small number of patients the sweat test result is in the ‘grey’ area: too high to be normal and too low to be called really abnormal. In these situations further diagnostic tests are necessary. Apart from sequencing of the whole CFTR gene one can measure the function of the chloride channel by a test in the nose. This test is only available in certain specialized centers. At the age of 2 years you can only do this test when a child is put to sleep: in the case of your daughter you should thus consult with your doctor what the best option is: being patient and wait for the results of the gene sequencing or having the nasal PD test done.

To answer your last question: can poor growth be caused by allergy. There are very many causes of poor growth in children. Allergy is not one of them. CF is a chronic disease so even children with a normal function of the intestine can have poor growth. Also here we think that you should share your concern about the poor growth of your child with your doctor and ask him what he thinks about it.
Yours sincerely,
Prof. K. De Boeck

26.01.2009