alpha-Fetoprotein and cystic fibrosis.

Because of unconfirmed reports that the serum level of alpha-fetoprotein (AFP) is high in children with cystic fibrosis and intermediate in their siblings and parents, this level was measured in 25 children with cystic fibrosis, 26 of their siblings, 42 of their parents and 31 age-matched children without cystic fibrosis who were attending outpatient clinics of the Montreal Children's Hospital. Liver function tests were performed at the same time since patients with liver disease may have unusually high serum AFP levels and patients with cystic fibrosis often have liver involvement. AFP was not detected in any of the serum samples, and the results of the liver function tests were normal in all but 1 individual, a control subject. In simultaneous assays of serum from children with ataxia telangiectasia, however, high AFP levels were detected in 15 of 16 samples. Thus, measurement of the serum AFP level is of no value in detecting carriers of the cystic fibrosis gene.