OKAY TS et al. Frequency of the ∆f508 mutation in 108 cystic fibrosis patients in São Paulo: comparison with reported Brazilian data. CLINICS 60(2):131-134, 2005. PURPOSE:To analyze the frequency of the delta F508 (∆F508) deletion mutation in 108 unrelated cystic fibrosis patients and compare the results with the previously reported data for Brazilian patients. Cystic fibrosis is the leading cause of genetic disease in Caucasians, and the ∆F508 deletion is the most common mutation associated with the disease.METHOD: The frequency of the ∆F508 mutation was assessed by means of a polymerase chain reaction (PCR) followed by detection in 8% silver-stained polyacrylamide gels.RESULTS: Twenty-three of 108 patients (21.3%) were homozygous for the ∆F508 deletion, 50 were heterozygous (46.3%), and the remaining 35 (32.4%) were non-carriers. In terms of alleles, there were 96 mutated (96/216 or 44.45%) and 120 wild-type ones (120/216 or 55.5%).CONCLUSION: The 44.45% of affected alleles that were found is higher than the 33% first described in 1993, but slightly lower than the 48% recently reported. Moreover, our data corroborated the idea that the frequency of the ∆F508 mutation is lower in Brazil in comparison to that found in studies carried out in Europe and North American (circa 70.0%), probably due to increased racial miscegenation. These findings must be taken into account before any genetic screening of the population is proposed in Brazil. CLINICS 60(2):131-134, 2005 Frequency of the ∆F508 mutation in 108 cystic fibrosis patients in são paulo Okay TS et al.