Important question to Cystic Fibrosis

Question

Dear ladies and gentlemen,
first of all a short prehistory:

our daughter, almost 4, is ill very often (2 pneumonias, 2 x the flu with Influenza B with a stay at the hospital), she has often a dry cough at night which turns to be productive then, often bronchitis and at the children convalescent care they diagnosed a mixed asthma, as she reacted strongly to cat, dog, rye, wheat, sage brush and other grasses and of course the permanent cough at night.
She is snoring at night and we should clarify if she has adenoids.
She only weighs about 16 kilogramms at a height of 110cm. She is very thin - but very tall for her age.
Last week we had a visit at the pulmonolgist and he arranged a sweat test.
We had today a second sweat test done. The last test was last week and the result was 55.
Today the result was 59 mmol/l.
After that we had a talk with the chief physician for pulmonolgy and allergology. After the result of 59 was obvious, we were already in panic that the physician would affirm the diagnosis Cystic Fibrosis.
The chief physician said that he excludes Cystic Fibroisis in the case of our daughter because firstly the results should be higher, but both have been under 60. He said that over 80 mmol/l one could be sure.
Secondly, he did an x-ray of the lung to our 4-year old daughter and stated that he could not see any changes, and a child, suffering from CF would have changes at the lung x-ray.
He even explained the x-ray to me.
I mentioned the genetic testing to him; he was of the opinion that if one has any doubts or both results would have been higher, he would advise the complex genetic testing, but he does not see any reason for this here, as other signs are lacking (however, from our point of view some do speak for this).
He was of the opinion that children with CF are permantly producing mucus, but our daughter had a free lung and is not permantly producing mucus.
Of course we are relieved in some way, but we do not have a 100% statement either, right?
I asked if we could have our genes checked, means my husband and me, and in case one of us does not carry the gene, one could exclude it for our daughter, but he was of the opinion that we should not worry about this and this was not necessary as he excludes it due to his investigations.
Can we rest assured or are the two times results of 55 and 59 a reason for concern? In case of CF are 2 x higher results expected or at leat one time?
The physician mentioned that it could be that one gene was there in our daughter, but it does not come out because she does not have it but it is only inside her. And then such results in the borderline zone could come out.
IN addition, blood has been taken from our daughter in order to control the immune system.
Sorry that the question has turned out so long, but I wanted to describe everything as detailed as possible to you in order that you could probably help us further, respectively that you can give us a statement if we have to worry or if the physician is right (according to the results and statements).

Many thanks in advance,

Answer

Hello,
at this point of time, the illness of CF is neither excluded securely, nor confirmed. The two results of the sweat test are lying in a so-called borderline area, that means the limit value of 60 has not been crossed.
From the mentioned symptoms it can be rather assumed that we do not have to deal with a typical CF in the case of this child. However, CF can not be excluded, as just in case of the rather untypical courses, the values of the sweat test can also be within the borderline area.
A genetic testing can be helpful in such cases, but unfortunately, however, can not always clarify the situation totally. In case mutations (changes in the gene) would be found in the CFTR-gene, which are known to be illness-causing, this would confirm the diagnosis CF. In case no mutations would be found, the diagnosis CF would be improbable but however not totally excluded, as in rare cases there could be mutations, which could not be detected by the conventional molecular genetic investigations.
A genetic testing can in this case therefore be helpful as it can either provide security for the presence of CF or can make it more improbable.
Besides the possiblity of a genetic testing, one should consider in the present case if a measurement of the so-called potential-difference at the nasal mucosa should be done. This measurement, however, could not exclude CF to 100% either. There are furhter diagnositc tools that can help to clarify the situation in case of two borderline sweat tests: analysis of the function of the pancreas (stool-fat, elastase in the stool) and microbiological investigation of the airways for example. Clinical symptoms can be a hint for making a diagnosis, an x-ray of the lung without any changes, however, can not generally exclude a CF.
Measurements of the potential-difference are only perforemd in some few CF centers. Genetic testing is offered by more than 50 laboratories in Germany, whereas only a part of the laboratories is doing a complete sequencing of the CFTR gene.

Yours sincerely,
Dr. Stuhrmann-Spangenberg

24.11.2008