Nutritional management of phenylalanine hydroxylase (PAH) deficiency in pediatric patients in Canada: a survey of dietitians' current practices

Recent Advances in Phenylketonuria: A Review

This article highlights the significance of inborn errors of metabolism and focuses specifically on phenylketonuria (PKU), a well-known inheritance disorder caused by the deficiency or absence of phenylalanine hydroxylase (PAH). This review discusses associated mutations in the PAH gene and their impact on phenylalanine metabolism. A total of 40 articles were analyzed between 2019 and 2023, covering diagnostic innovations, advancements in treatment and management strategies, and the long-term implications of PKU. This study emphasizes the importance of early diagnosis and highlights the ongoing need for advancements in screening methods and treatment approaches to optimize patient outcomes in PKU patients. This review provides valuable insights for healthcare professionals involved in the care of children with PKU and contributes to the enhancement of clinical practice in this field.

Knowledge and perception of inborn errors of metabolism (IEMs) among healthcare students at a selected public university in Klang Valley, Malaysia

Healthcare providers play an important role in improving the health of Inborn Error of Metabolism (IEM) patients. However, IEM knowledge level among local healthcare students has yet to be determined. Thus, the aim of this study is to assess the knowledge and perception of IEM among local healthcare students. An online self-administered questionnaire was distributed to 378 students across the Faculty of Health Science, Pharmacy and Dentistry from a selected public university in Lembah Klang, Malaysia. For knowledge, a score of 1 is assigned to each correct answer with a maximum total score of 14. Likert scale was used to determine their perception of IEM. The total mean score of IEM knowledge among healthcare students is 5.8. There was no significant difference of mean score of IEM knowledge among the students from the Faculty of Health Science (6.1 ± 2.7), Pharmacy (5.5 ± 2.6) and Dentistry (5.8 ± 2.8). However, the score of knowledge is observed to be significantly different by ethnicity, religion and family history of IEM (p < 0.05). Furthermore, students with experience of meeting an IEM patient and attending IEM classes scored higher than those with no experience (p < 0.05). Most of the healthcare students (89.5%) perceived their knowledge to be insufficient and very poor. Majority of the students from faculty of pharmacy (70.8%) agreed that the IEM course should be mandatory compared to health sciences and dentistry (p < 0.05). This study identified an overall inadequacy of knowledge of IEM among healthcare students. There is a pressing need to improve the IEM-related knowledge and awareness of Malaysian healthcare students. This can be accomplished by incorporating online classes that emphasizes the treatment and management of IEMs in the university curriculum.

Defining tetrahydrobiopterin responsiveness in phenylketonuria: Survey results from 38 countries

BACKGROUND

A subset of patients with phenylketonuria benefit from treatment with tetrahydrobiopterin (BH4), although there is no consensus on the definition of BH4 responsiveness. The aim of this study therefore was to gain insight into the definitions of long-term BH4 responsiveness being used around the world.

METHODS

We performed a web-based survey targeting healthcare professionals involved in the treatment of PKU patients. Data were analysed according to geographical region (Europe, USA/Canada, other).

RESULTS

We analysed 166 responses. Long-term BH4 responsiveness was commonly defined using natural protein tolerance (95.6%), improvement of metabolic control (73.5%) and increase in quality of life (48.2%). When a specific value for a reduction in phenylalanine concentrations was reported (n = 89), 30% and 20% were most frequently used as cut-off values (76% and 19% of respondents, respectively). When a specific relative increase in natural protein tolerance was used to define long-term BH4 responsiveness (n = 71), respondents most commonly reported cut-off values of 30% and 100% (28% of respondents in both cases). Respondents from USA/Canada (n = 50) generally used less strict cut-off values compared to Europe (n = 96). Furthermore, respondents working within the same center answered differently.

CONCLUSION

The results of this study suggest a very heterogeneous situation on the topic of defining long-term BH4 responsiveness, not only at a worldwide level but also within centers. Developing a strong evidence- and consensus-based definition would improve the quality of BH4 treatment.

Validation of plasma amino acid profile using UHPLC-mass spectrometer (QDa) as a screening method in a metabolic disorders reference centre: Performance and accreditation concerns

INTRODUCTION

Amino acid (AA) analysis in plasma is essential for diagnosis and monitoring of inborn errors of metabolism (IEM). The efficacy of patient management is governed by the rapidity of AA profile availability, along with the robustness of the method. French quality guidelines and progress made in analytical techniques have led biologists to develop AA profile exploration via mass spectrometry (MS).

OBJECTIVES

The aim of this study was to validate an analytical method with a single quadrupole mass spectrometer (MS) and to suggest reference values in regard to French quality and IEM society recommendations.

DESIGN AND METHODS

Plasma samples from patients were deproteinised and derivatised with AccqTag™ reagent. Analysis was performed by reverse-phase chromatography coupled to QDA detector. We evaluated accuracy, intra-days and inter-days precision and limit of quantification by the β-expectation tolerance interval method for 27 AA. Method comparison was performed with the standard method (ion exchange chromatography, IEC) on Jeol Aminotac® and to tandem MS. Reference values were established on AA concentrations of the cohort of patients who had no IEM.

RESULTS

Our method allowed the separations of almost all amino acids with a total run time of 12 min. Separation of isoleucine and alloisoleucine was incomplete (R = 0.55) but without impact on biological interpretation. Precision, accuracy and quantification were satisfactory (intra-days coefficient of variation (CV) was <5%, inter-days precision CV <10% and accuracy <15%). The limits of quantification were validated between 1 and 900 µmol/L. Results were comparable between the new method and IEC.

CONCLUSION

Ultimately, we validated a rapid method on plasma for quantifying 27 amino acids that can be used in routine practice, according to French quality laboratories and SFEIM (French Society of Inborn Error of Metabolism) recommendations. Furthermore, estimated reference values were similar to those found in published studies focusing on other methods. Despite a lower specificity compared to tandem MS, the simplicity and rapidity of our method are the main advantage of this technique and place it as a major tool in IEM diagnosis and management.

Developments in evidence creation for treatments of inborn errors of metabolism

Inborn errors of metabolism (IEM) represent the first group of genetic disorders, amenable to causal therapies. In addition to traditional medical diet and cofactor treatments, new treatment strategies such as enzyme replacement and small molecule therapies, solid organ transplantation, and cell-and gene-based therapies have become available. Inherent to the rare nature of the single conditions, generating high-quality evidence for these treatments in clinical trials and under real-world conditions has been challenging. Guidelines developed with standardized methodologies have contributed to improve the practice of care and long-term clinical outcomes. Adaptive trial designs allow for changes in sample size, group allocation and trial duration as the trial proceeds. n-of-1 studies may be used in small sample sized when participants are clinically heterogeneous. Multicenter observational and registry-based clinical trials are promoted via international research networks. Core outcome and standard data element sets will enhance comparative analysis of clinical trials and observational studies. Patient-centered outcome-research as well as patient-led research initiatives will further accelerate the development of therapies for IEM.

Variants of the phenylalanine hydroxylase gene in neonates with phenylketonuria in Hainan, China

OBJECTIVE

To investigate the incidence of phenylalanine hydroxylase (PAH) deficiency and PAH genotypes in neonates in Hainan, China. Methods: We performed heal stick to collect blood and obtain dry blood spot specimens from newborns in Hainan from January 2007 to December 2016. Phenylalanine (Phe) concentration in these dry blood spots was measured by the fluorescence method to screen phenylketonuria (PKU). For suspicious samples, the genotypes of the PAH gene were amplified by biotin labeled oligonucleotide primers. Polymerase chain reaction (PCR) products were then analyzed by flow-through hybridization to detect genotypes. At the same time, peripheral blood samples of children suspicious of PKU and their parents were used to perform gene sequencing. Results: Of the 914,520 newborns screened, 29 of them had PAH deficiency. The incidence of PAH deficiency in Hainan was 3.17/100,000. A total of 58 mutant alleles belonging to 15 different types were identified in the 29 patients. In terms of genotypes frequency, the top 4 were: c.611A > G 20.7% (12/58) , c.728G > A 17.2%, c.158G > A 15.2% (9/58) and c.721C > T 13.8% (8/58). The frequencies of other genotypes were all below 10%. Conclusion: The incidence of PAH deficiency in Hainan is relatively high among all provinces in southern China. With a total frequency of 67.2%, c.611A > G, c.728G > A, c.158G > A and c.721C > T, and are the most common PAH gene genotypes.