Cystic fibrosis (CF or mucoviscidosis) is a common recessive genetic disease with approximately 4% of the Caucasian population in Europe carrying one or more cystic fibrosis alleles. The disease develops when both genes are defective and the median age of survival is around 30 years.
The leading cause of morbidity and mortality is a progressive decline in pulmonary function resulting from airway damage caused by thickened secretions complicated by chronic microbial infection. In addition, about 85% of CF patients develop insufficiency of the exocrine pancreas that necessitates lifelong administration of dietary enzyme supplements.
Diagnosis of the disease frequently takes place when symptoms are already obvious, rather than in very early stages, thereby delaying disease management and allowing disease progression to do considerable harm. Over 10% of the population is diagnosed at a point when damage is already irreversible.
Cystic fibrosis is routinely diagnosed by newborn screening for immuno-reactive trypsinogen (IRT), complemented by sweat testing. The newborn screen initially measures for raised blood concentration of IRT. Because of false-positive and negative tests from carriers and individuals with mild mutations in the CFTR gene, CF screening in newborns can be controversial. Diseases like AIDS, suprarenal capsule dysfunction, atopic dermatitis, Down’s syndrome, adrenogenital syndrome and coeliac disease can also lead to a false-positive sweat test result.
In order to get more reliable CF diagnosis genetic testing is ultimately required. CF can result from more than a thousand different mutations, and it is not yet possible to test for each one.
However, a high risk CF group is characterized by a presence of about 20 (depending on the population) most frequent common mutations with a strong CF phenotype. Best practice guidelines for molecular genetic diagnosis of cystic fibrosis and CFTR-related disorders (updated European recommendations) have been developed and published in 2009.  The suggested panel of CF-causing mutations for population or prenatal screening of Caucasians consists of 17 mutations, each of which is found with a frequency of more than 0.1%.