Retrospective, observational data collection of the treatment of phenylketonuria in the UK, and associated clinical and health outcomes

Abstract

Objective:

To determine the percentage of phenylketonuria (PKU) subjects using current treatment strategies whose phenylalanine (Phe) concentrations diverge from the UK target guidelines for PKU.

Research design and methods:

This retrospective, observational, chart review was conducted between 2004 and 2008 at three specialist PKU treatment centres in the UK, and included 125 eligible subjects: 20 adults (18+ years, with ≥4 Phe concentrations measured per year) and 105 children (up to age 17, with ≥6 Phe concentrations measured per year).

Results:

The mean percentage of subjects with at least 70% of Phe concentrations within the target range for 0–5-year olds, 6–10 year olds and 11–17 year olds was similar across the period 2004–2008 (57.0%, 56.5% and 57.1%, respectively) and lower (39.4%) in the 18+ year age group. For all ages, across the period the mean was 54.4%. Further analysis of the adult population showed that some subjects were very good at complying with treatment and reporting Phe concentrations. Overall, the percentage of 100% compliance was 15.7% in females and 13.7% in males. The mean duration that subjects were ‘out of range’ of target Phe concentrations over the study period was approximately 1 year and 3 months and the mean duration for ‘significantly out of range’ values was approximately 9 months. The most common type of contact made with subjects was by telephone, with a mean number of 16 calls per subject per year.

Conclusion:

The results support current literature showing that a proportion of subjects with PKU, in particular older subjects, are not fully compliant with their treatment and subsequently have Phe concentrations that depart from national recommendations. However, definitive conclusions may not be drawn due to the retrospective nature of the study and the small number of observed subjects.

Key words::

• Diet
• Hyperphenylalaninaemia
• Metabolic
• Phenylalanine
• Phenylketonuria
• PKU
• Uncontrolled

Transparency

Declaration of funding

This study was sponsored by Merck-Serono.

Declaration of financial/other relationships

A.D. has disclosed that she has received compensation from Merck Serono as a member of the European Nutritionist Expert Panel in PKU and as a member of the Scientific Advisory Board on PKU. She has also received honoraria for consulting or lecturing from SHS International, Nutricia and Merck Serono. She has received research grant funding from Vitaflo International, Nutricia and SHS International. K.N., L.P., M.N. and D.C. have disclosed that they are employed by Merck Serono. CMRO peer reviewers may have received honoraria for their review work. The peer reviewers on this manuscript have disclosed that they have no relevant financial relationships.

Acknowledgements

The authors thank Dr Peter Galloway (Glasgow Royal Infirmary), Dr Andrew Morris and dietician Fiona White (Royal Manchester Children’s Hospital) for their support with this study and contribution to data collection.

Medical writing of this article was performed by freelance medical writer, Dr Samina Hamilton of Sam Hamilton Medical Writing Services Limited, Newcastle Upon Tyne, UK. Statistical analysis of the data was performed by Tal Otiker of the Contract Research Organisation, Satellite Outsourcing, South Ruislip, Middlesex, UK. Merck-Serono reimbursed these contributors for their services.