CF

Question

If you have been tested for CF as a child and this result was negative, can you then still get cystic fibrosis later on.

Answer

Thank you for this important question. There are two aspects to the question and the answer: what is cystic fibrosis and with which test can one check if a person is suffering from cystic fibrosis.

Cystic Fibrosis is a disease with a very variable pattern: from serious classical disease to very mild atypical forms. You can read more about this under the topic “diagnosis”.
There are several tests that evaluate a possible diagnosis of cystic fibrosis and also our interpretation of what is a normal and a abnormal test result has evolved over the years. The most used test is the sweat test. In people with classical cystic fibrosis (early onset of symptoms, digestive problems, infectious of the airways) this test is clearly positive. This means that the chloride content will be higher 60 mmol/L. In the meantime we have learned that some patients have a lower sweat chloride value (between 30-60 mmol/L and sometimes even lower than 30 mmol/L) in whom we can demonstrate with very specific tests that they still do have a cystic fibrosis like disease. The second test used in diagnosis is mutation analysis. There are more than 1500 different mutations or errors in the CFTR gene that are known. Some errors have more serious consequences than others. Read more about this under the heading “genetics”.
The third test that we use in the diagnosis of cystic fibrosis checks in the patient how active his chloride channel is. Cystic fibrosis is indeed a disease where a certain salt channel through which negative loaded particles travel to the outside (chloride) doesn’t work.

The answer to your question is thus clear. You are born with cystic fibrosis but sometimes the consequences of the disease only become apparent later in your life. It could thus be that the doctor has new arguments to check if you could have a mild form of the disease cystic fibrosis. That means the doctor might want to repeat an old test or use one of the newer more sensitive tests to be certain that the complaints that a certain person has are the consequences of cystic fibrosis or one of its milder variants.

Kind regards
Prof. Dr. K. De Boeck

14.09.2010