DNA

Question

How many DNA variants are examined when CF is suspected?

Answer

At the moment, more than 1.600 mutations or variants are known in the CFTR gene. One mutation is the most common: F508del accounts for about 70% of all mutations (to a lesser extent in more southern countries). A routine test looking for 30 to 35 additional mutations covers for 88-92% of all mutant CFTR genes possibly leading to CF. This figure holds true for Belgium, the Netherlands etc… In the more southern European countries, commercial genetic testing cover a lower percentage of prevalent mutations. With a routine CFTR test, the most frequent mutations are thus looked for, covering for 88-92% of all defect CFTR genes. Local or national laboratories can decide to look for specific mutations that are common in a certain area or country. In that way, mutations or variants investigated can be adapted depending on the country of origin. A negative testing result does therefore not mean that the presence of a CF mutation can be fully excluded. There is still a low residual risk that a severe CF mutation is present, not detected in a routine test. If CF is suspected and routine DNA screening is negative, further investigations can be applied for, including additional DNA testing to investigate for a possible cystic fibrosis disease.
H. Cuppens.

23.03.2010