A comprehensive integrated disease management program for phenylketonuria (IDMP-PKU) from Türkiye: rationale, design and patient characteristics

Abstract

Background: Phenylketonuria is an autosomal recessive disorder characterized by the deficiency of phenylalanine hydroxylase, which converts phenylalanine into tyrosine. Diagnosis and prompt initiation of appropriate treatment shortly after birth are important for achieving optimal outcomes in phenylketonuria. IDMP-PKU is an ongoing study to gain insight into the patient journey and identify the unmet needs and areas for improvement in diagnosis, treatment, and follow-up of PKU in Türkiye.

Aim: To present the rationale and design of the IDMP-PKU study, as well as the findings from an interim analysis, describing baseline demographic, diagnosis, family history, and genetic testing data for 1553 children enrolled in the study.

Method: This is a multicenter, observational registry-based study, conducted in 3 tertiary pediatric metabolic clinics in Türkiye. The study provides a descriptive analysis of baseline demographic, diagnosis, family history, and genetic testing data of study population.

Results: The study included 1,553 patients (median age: 10 (IQR 5-18) years; 37.1% classical PKU) from 90% of the cities in Türkiye, diagnosed between 1981 and 2022. Parental consanguinity was reported in 43.5% of families (27.1% first cousins). The most frequently detected allelic variant was c.1066-11G > A (IVS-10-11G > A) (22.8%). Homozygous mutations were more common in patients with parental consanguinity (76.8% vs 17.1%; p < 0.001). The median time to diagnosis improved to 21 days after the implementation of the national newborn screening (NBS) program in December 2006 but 28.6% of patients were diagnosed after one month of age. Low level of maternal education was associated with longer time to diagnosis (p < 0.001).

Conclusions: Implementation of national NBS has contributed to earlier identification of patients with PKU. Increasing the number of screening laboratories and pediatric metabolic clinics will speed up the diagnostic process and help achieve the guideline-recommended time for diagnosis and initiation of treatment. In countries with high rates of consanguineous marriages, increasing public awareness of PKU and genetic counselling before marriage will be valuable in reducing the prevalence of PKU.

Keywords: Allelic variant; Consanguinity; Diagnosis; Maternal education; Newborn screening; Phenylketonuria.

Fig. 1

Method of HPA (Hyperphenylalaninemia)/PKU (Phenylketonuria) diagnosis (n = 1,522). Number of newly diagnosed patients has increased as of the initiation of pilot newborn screening program (NBS) in 1985. A prominent increase occurred after the implementation of national NBS in December 2006 (colour should be used for this figure)

Fig. 2

Time to HPA/PKU diagnosis by year of diagnosis (days) (n = 1522). Red and green lines in the figure denote the introduction of the pilot and national NBS for PKU. (colour should be used for this figure)