Blood phenylalanine control in phenylketonuria: A survey of 10 European centres

Background: Only limited data are available on the blood phenylalanine (Phe) concentrations achieved in European patients with phenylketonuria (PKU) on a low-Phe diet.Objective: A survey was conducted to compare blood Phe control achieved in diet-treated patients with PKU of different age groups in 10 European centres.Methods: Centres experienced in the management of PKU from Belgium, Denmark, Germany, Italy, The Netherlands, Norway, Poland, Spain, Turkey and the United Kingdom provided retrospective audit data of all patients with PKU treated by diet over a 1-year period. Standard questions were used to collect median data on blood Phe concentrations, percentage of blood Phe concentrations below upper target reference ranges and frequency of blood Phe sampling.Results: Data from 1921 patients on dietary management were included. Blood Phe concentrations were well controlled and comparable across centres in the early years of life. The percentages of blood Phe concentrations meeting each centre's local and national target ranges were 88% in children aged up to 1 year, 74% for 1-10 years, 89% for 11-16 years and 65% for adults (>16 years). The frequency of home blood sampling, compared with local and national recommendations for monitoring Phe concentrations, appeared to decline with age (from approximately 100% in infancy to 83% in teenagers and 55% in adults).Conclusions: Although blood Phe control generally deteriorated with age, some improvement was observed in adolescent years across the 10 European centres. The blood Phe control achieved seemed comparable in many of the European centres irrespective of different dietary treatments or national policies.