Abstract
Early dietary treatment of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, results in normal cognitive development. Although health-related quality of life (HRQoL) of PKU patients has been reported as unaffected in high-income countries, there are scarce data concerning HRQoL and adherence to treatment of PKU children and adolescents from Brazil. The present study compared HRQoL scores in core dimensions of Brazilian early-treated PKU pediatric patients with those of a reference population, and explored possible relationships between adherence to treatment and HRQoL. Early-treated PKU pediatric patient HRQoL was evaluated by self- and parent-proxy reports of the Pediatric Quality of Life Inventory (PedsQL) core scales. Adherence to treatment was evaluated by median Phe levels and percentage of results within the therapeutic target range in two periods. Means for total and core scales scores of PedsQL self- and parent proxy-reports of PKU patients were significantly lower than their respective means for controls. Adequacy of median Phe concentrations and the mean percentage of values in the target range fell substantially from the first year of life to the last year of this study. There was no significant difference in mean total and core scale scores for self- and parent proxy-reports between patients with adequate and those with inadequate median Phe concentrations. The harmful consequences for intellectual capacity caused by poor adherence to dietary treatment could explain the observed decrease in all HRQoL scales, especially in school functioning. Healthcare system and financial difficulties may also have influenced negatively all HRQoL dimensions.
Highlights
Phenylketonuria (PKU, OMIM 261600) is an autosomal recessive inborn error of phenylalanine metabolism, caused by a deficient activity of phenylalanine hydroxylase (PAH, EC 1.14.16.1) – an enzyme that coverts the essential amino acid phenylalanine (Phe) to tyrosine, leading to an accumulation of Phe in blood and other tissues [1]
health-related quality of life (HRQoL) PedsQL self-reports were administered to 49 earlytreated PKU patients aged 6 to 17 years – self-reports could not be administered to 2 patients (1 refused to answer the questionnaire and the other was not able to fill it out owing to intellectual disability)
Lower scores were obtained for almost all the generic core scales for PedsQL self-reports and parent-proxy reports of PKU children and adolescents when compared to a normative sample of healthy Brazilian schoolchildren
Summary
Phenylketonuria (PKU, OMIM 261600) is an autosomal recessive inborn error of phenylalanine metabolism, caused by a deficient activity of phenylalanine hydroxylase (PAH, EC 1.14.16.1) – an enzyme that coverts the essential amino acid phenylalanine (Phe) to tyrosine, leading to an accumulation of Phe in blood and other tissues [1]. In Latin America, it was estimated an incidence of PKU of about 1:21,000 live births (1:12,000 to 1:52,000) [3]. In Brazil, the incidence of PKU was reported as approximately 1 in 25,000 live births [4], there are important variations among different Brazilian states, from 1:9,000 to 1:33,000 [5,6,7,8,9]. The establishment of mass newborn screening programs allowed the detection of PKU in the neonatal period and the early establishment of dietary treatment, resulting in a normal cognitive development [10]. In 2001, the National Neonatal Screening Program was established within the Brazilian National Health System, ensuring access of all newborns to screening, confirmatory tests, and treatment for PKU, including the provision of metabolic phenylalanine-free formula [4]
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