Comprehensive analysis of 1103 infants referred to a single center due to positive newborn screening test for phenylketonuria.

Abstract

Objective: Phenylketonuria (PKU) is a prevalent inherited metabolic disorder, resulting from biallelic pathogenic variants in the PAH gene. This study aimed to assess the clinical characteristics of 1103 infants referred to a single center due to positive newborn screening (NBS) tests for PKU, providing insights into screening and diagnosis.

Methods: The health records of infants who were referred with suspicion of PKU through the Turkish national NBS program to a single referral center between January 2016 and January 2023 were retrospectively reviewed. The study analyzed demographic data, clinical findings, and diagnostic results from hospital records. Logistic regression analysis identified significant predictors of age at admission.

Results: This study highlights significant regional differences within Türkiye regarding DBS collection, result reporting, and age at admission. Significant delays in age at admission (expressed as median, [Q1-Q3]) were noted in the Eastern Anatolia (34 days [27-42]), Southeastern Anatolia [34 days (25-42)], and Black Sea regions [26 days (19-33)]. Out of the referred infants, 5.1% and 2.4% had transient tyrosinemia and transient hyperphenylalaninemia, respectively, and these transient conditions were more prevalent among neonates with a history of jaundice. Phenylalanine level was normal in 38.1% of the patients and was considered false positive. Among the 26 (2.36%) patients admitted after 90 days (late admissions), there were 2 PKU patients with untreated Phe levels >20 mg/dL (n=2). Among the 140 infants requiring treatment, 1.43% (n=2) were late admissions (>90 days). A history of PKU in the family and higher initial Phe levels were associated with earlier admissions.

Conclusion: This comprehensive analysis underscores the need to enhance NBS programs, particularly in regions with identified delays. Improving healthcare infrastructure, increasing awareness, and implementing targeted health policies are crucial for timely diagnosis and treatment. Future research should address regional disparities and optimize screening protocols to improve outcomes for affected infants.