Dietary compliance during bh4 loading test in patients with phenylketonuria

Abstract

In Phenylketonuria (PKU), prior to BH4 treatment, a loading test (BH4-LT) is usually necessary to determine responsiveness. The Portuguese Society of Metabolic Disorders advocate a 72h BH4-LT. Concurrently with a BH4-LT, a strict dietary protocol should be followed, but adherence with this is rarely reported. The aim of this study was to compare prescribed natural protein (NP, g/kg), Phenylalanine (Phe, mg/kg), L-amino acid supplements (AA, g/kg) and total protein (TP, g/kg) with reported dietary intake during 72h BH4-LT’s. The sample included 78 PKU patients (20.9 ± 9.1 y; 4-48 y; 51% females; 41% classical PKU, 49% mild PKU, 4% hyperphenylalaninemia and 6% late diagnosed) who had a BH4-LT between March 2015 and January 2017. Potential BH4 responsiveness was considered with a blood [Phe] reduction ≥ 30%. Anthropometry, NP, Phe intake, AA and TP prescriptions were documented. A 3-day diet diary was used to calculate mean daily nutritional intake during BH4- LT and to compare with diet prescription. Prescribed NP and Phe were similar with reported nutritional intakes during BH4-LT (0.80 ± 0.46 vs. 0.77 ± 0.44 g/kg, p=0.106; 38.13 ± 22.74 vs. 36.73 ± 21.37 mg/kg, p=0.116, respectively). In contrast, reported AA and TP intakes were significantly lower compared with dietary prescription (1.01 ± 0.37 vs. 1.05 ± 0.35 g/kg, p=0.006; 1.64 ± 0.49 vs. 1.71 ± 0.49 g/kg, p=0.003, respectively). Potential BH4 responders (n=33) reported Phe and NP intakes in accordance with dietary prescription (43.10 ± 24.41 vs. 43.37 ± 24.26 mg/kg, p=0.922; 0.90 ± 0.50 vs. 0.91 ± 0.49 g/kg, p=0.721, respectively), while non-responders (n=45) reported lower Phe and TP intakes (32.05 ± 17.69 vs. 34.30 ± 21.00 mg/kg, p=0.048; 1.57 ± 0.50 vs. 1.66 ± 0.50, p=0.004, respectively). Children (n=29) had reported ingestions compliant with dietary prescription and adults (n=49) had a mean intake of AA and TP during the BH4-LT inferior to the amounts prescribed (0.94 ± 0.37 vs. 1.00 ± 0.35, p=0.007; 1.47 ± 0.39 vs. 1.56 ± 0.46, p=0.018, respectively). 57 of 78 patients (73.1%) reported ingestion of non-prescribed food items: e.g. soft drinks (47.4%), cakes and sweet desserts (26.3%) and potato chips (24.6%). The results demonstrated incomplete dietary adherence with prescribed dietary protocols during BH4-LT. It is important to fully monitor and support patients during BH4-LT to ensure adequate consumption of prescribed NP, TP and AA in order to aid accuracy of outcome with BH4-LT.

Date of Award	15 May 2018
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Júlio César Leite da Fonseca Rocha (Supervisor) & Rui Barros (Co-Supervisor)