DNA analysis of cystic fibrosis in Brazil by direct PCR amplification from Guthrie cards

A 3 bp deletion of condon 508 (phenylalanine) of the cystic fibrosis (CF) gene constitutes the mutation of most CF chromosomes. The frequency of this mutation (referred to as ΔF508), varies considerably between populations, ranging form 26% of the CF mutations in Turkey to 88% in Denmark. To determine the frequency of the ΔF508 mutation in Brazilian Caucasoid CF patients, we used direct polymerase chain reacion (PCR) amplification of DNA obtained from dried blood spots on Guthrie cards, followed by ethidium bromide staining of gels. Although the overall frequency of the ΔF508 mutation was 47% of 380 CF chromosomes from Brazilian Caucasoids born in five different states, significant inter-state differences were observed, ranging from a ΔF508 frequency of 27% to 53%. While our method could be used to screen patients and their relatives for carrier testing and prenatal diagnosis, the efficacy of screening only for the ΔF508 mutation would be low, and would vary from state to state. Screening for a panel of local mutations will be needed to increase the mutation detection rate and optimize genetic counseling. © 1993 Wiley-Liss, Inc.