Factors influencing verbal intelligence and spoken language in children with phenylketonuria

Abstract

Objectives: To determine verbal intelligence and spoken language of children with phenylketonuria and to study the effect of age at diagnosis and phenylalanine plasma level on these abilities. Design: Cross-sectional. Setting: Children with phenylketonuria were recruited from pediatric hospitals in 2012. Normal control subjects were recruited from kindergartens in Tehran. Participants: 30 phenylketonuria and 42 control subjects aged 4- 6.5 years. Skills were compared between 3 phenylketonuria groups categorized by age at diagnosis/treatment, and between the phenylketonuria and control groups. Main outcome measures: Scores on Wechsler Preschool and Primary Scale of Intelligence for verbal and total intelligence, and Test of Language Development-Primary, third edition for spoken language, listening, speaking, semantics, syntax, and organization. Results: The performance of control subjects was significantly better than that of early-treated subjects for all composite quotients from Test of Language Development and verbal intelligence (P >0.001). Early-treated subjects scored significantly higher than the two groups of late-treated subjects for spoken language (P =0.01), speaking (P =0.04), syntax (P =0.02), and verbal intelligence (P =0.019). There was a negative correlation between phenylalanine level and verbal intelligence (r= �0.79) in early-treated subjects and between phenylalanine level and spoken language (r= �0.71), organization (r= �0.82) and semantics (r= �0.82) for late-treated subjects diagnosed before the age one year. Conclusion: The study confirmed that diagnosis of newborns and control of blood phenylalanine concentration improves verbal intelligence and spoken language scores in phenylketonuria subjects. © 2015, Indian Academy of Pediatrics