Abstract

Phenylketonuria (PKU) is a rare metabolic disorder. Mutations in the enzyme phenylalanine hydroxylase (PAH), impair phenylalanine (Phe) metabolism into tyrosine, and a Phe build up in the brain causes neurological deterioration and consequently brain damage and developmental delay, if treatment is not initiated early. Treatment consists of a low protein diet restricted in the amino acid Phe. Diet is based on low protein foods, usually fruits and vegetables, together with a protein substitute to secure protein needs and special low protein foods to attain energy requirements. Sapropterin dihydrochloride (BH4), is a synthetic form of the co-factor tetrahydrobiopterin, necessary for the PAH activity. Patients who respond to the drug can increase Phe tolerance, leading to diet relaxation and consequently more natural protein introduction in the diet, and/or can improve metabolic control of patients. However, reports of patients’ food patterns in PKU are scarce, with existing ones reporting increase intake of known familiar foods and neophobia to new protein sourced foods. This could lead to nutritional imbalances, particularly in micronutrient status. A retrospective observational longitudinal study will be performed in a cohort of paediatric (0-17 years) PKU patients followed at the BCH, and their caregivers. Data from patients records (age, gender, diagnosis, weight, height, BMI, metabolic control) food frequency and food neophobia questionnaires will be collected. From caregivers an anxiety and depression questionnaire willbe applied. We expect these results to be of extreme importance to characterize food patterns and food choices in children treated with BH4 treatment as well as their caregivers’ burden.

METHODOLOGY

This study will be performed at the Birmingham Children’s Hospital in Birmingham (BCH), England. The study design is observational, longitudinal and retrospective. Data from a cohort of paediatric PKU patients (0-17 years) followed-up at BCH, responsive to BH4, and data from their caregivers, will be collected and treated.
Data collection from patients’ records and caregivers’ will be made retrospectively, from September to December 2022. Data will be collected from patient’s records, specifically: personal data (age, gender, PKU diagnosis) anthropometry (weight, height, BMI), metabolic control (Phe measurements), questionnaire scores (Food Frequency Questionnaire, Food Neophobia Questionnaire). From caregivers’ we will collect data on the Hospital Anxiety and Depression (HADS) questionnaire and additional questions related to stress management with child. These will be organized under coded names on an Excel® spreadsheet.
The three questionnaires (food frequency, food neophobia and anxiety and depression), will be applied in three moments – at baseline (before BH4 loading test), 3 months after BH4 initiation and 6 months after BH4 initiation.
Statistically, we would like to characterize differences in the number of portions of food groups, during BH4 treatment. In the food neophobia questionnaire we would like to see the changes in children’s feelings toward food and experience of new foods during BH4 and in the anxiety and depression questionnaire which will be applied to children’s caregivers, will comprise of questions related to stress feelings.
There are no risks to participants. Inconvenience comprises only minimal increase length of dietetic appointment on questionnaires application and focus groups dynamics organized with caregivers. This project integrates routine clinical practice that would already be performed by the metabolic dietetics team at BCH on PKU treatment management.
Data protection: Patient records will be collected from the BCH database and participants’ personal data and the result variables described, will be stored under coded names on an Excel spreadsheet, and managed only by the project researchers. Answered food frequency questionnaires will be kept within the BCH dietetic department. Data management, treatment, and disposal will follow the General Data Protection Regulation.
Expected results Characterization of food patterns in PKU is of the utmost importance, particularly when a new treatment is added to disease management. We hope this work will provide new insight for health professionals, particularly dietitians and physicians, on PKU management with adjuvant treatments such as BH4 and Pegvaliase. We expect food choices to be altered with BH4 introduction and hope to demonstrate how patients make these choices while working to promote increased intakes of nutritionally dense foods to achieve optimal health with a more liberated diet. As we mentioned earlier, there are reports of nutrient imbalances when new drugs are added to treatment, and since this has a direct impact on patients nutritional status, to understand and prevent these through proper nutritional guidance is vital. Additionally, trends of intake in PKU patients under diet relaxation are important to look at to understand and personalize patient care. Factors influencing food choices such as social environment, socioeconomic status, culture, parental stress, etc. could eventually impact on diet relaxation and food patterns as well. Thus, at the end of this audit, and with the subsequent results, we also aim to develop a protocol to properly guide patients through food pattern changes.

EXPECTED RESULTS

Characterization of food patterns in PKU is of the utmost importance, particularly when a new treatment is added to disease management. We hope this work will provide new insight for health professionals, particularly dietitians and physicians, on PKU management with adjuvant treatments such as BH4 and Pegvaliase. We expect food choices to be altered with BH4 introduction and hope to demonstrate how patients make these choices while working to promote increased intakes of nutritionally dense foods to achieve optimal health with a more liberated diet. As we mentioned earlier, there are reports of nutrient imbalances when new drugs are added to treatment, and since this has a direct impact on patients nutritional status, to understand and prevent these through proper nutritional guidance is vital. Additionally, trends of intake in PKU patients under diet relaxation are important to look at to understand and personalize patient care. Factors influencing food choices such as social environment, socioeconomic status, culture, parental stress, etc. could eventually impact on diet relaxation and food patterns as well. Thus, at the end of this audit, and with the subsequent results, we also aim to develop a protocol to properly guide patients through food pattern changes.