Parental perceptions of cognitive skills used in daily functioning in children with PKU and the relationship to IQ, school grades, and blood phenylalanine measures
Authors:   , Askinazi Lauren S. 
Published: July 2024

To date, research examining cognitive and academic functioning in children with Phenylketonuria (PKU) has focused primarily on the use of traditional psychometric tests to assess level of functioning, while there have been limited studies that have examined the quality and level of perceived daily functioning. Studies using traditional psychometric tests have shown that despite scores in the normal range on intellectual measures, some early-treated children with PKU exhibit academic, neuropsychological, psychological and behavioral problems (Saudubray et al., 1987; Sullivan & Chang, 1999; Waisbren et al., 1994), as well as a higher incidence of abnormalities on MRI scans (Lou et al., 1992; Pietz et al., 1996). Thus, there is evidence that children with PKU may be at higher risk for displaying subtle deficits that are not being detected with traditional intelligence tests. However, it is unnecessary to perform more in depth neuropsychological testing on all children with PKU. It may be more practical to use a screening technique that parents can quickly complete during a routine visit to the PKU medical clinic. The current study utilized a brief informal measure of parental perceptions of daily functioning to screen for potential areas of concern in the development of general cognitive and academic skills of children with PKU. In this study, daily functioning is defined as the cognitive skills and behaviors that are necessary for children to perform efficiently in their everyday lives, including home and academic settings. A wide variety of abilities used in daily functioning were assessed using the Parent Rating Scale of Everyday Cognitive and Academic Abilities (PRSECAA). Subjects (age range 6-17) included a combined Classical and Atypical PKU group (n = 45), a group with Mild Hyperphe (n = 15), and a group of normal controls (n = 47). In contrast to the study hypothesis, the Mild Hyperphe group was found to have greater perceived difficulties in comparison to the normal control group on subscales from the PRSECAA used to assess memory & learning [F (2, 104) = 6.26, p = .003] and higher cognitive abilities [F (2, 104) = 5.42, p = .003], although their scores were still within the "normal" range (i.e., within 2 standard deviations of the control group). The Classical/Atypical group did not significantly differ from the normal controls on any of the scales. The current results suggest that despite having what was previously considered a "benign" form of PKU, children with Mild Hyperphe may have greater cognitive problems in comparison to normal controls. This study also examined the relationship between daily functioning skills and more formal measures of intellectual and academic functioning. Results suggest that parents are generally accurate raters of their children's skills [i.e., significant negative correlations were obtained between problems in daily functioning and estimated IQ scores from the WISC-III (r = -.28, p = .01) and school grades (r = -.38, p = .001)]. Lastly, this study examined the relationship between blood phenylalanine levels and daily functioning skills. As hypothesized, there were no significant correlations between phenylalanine level at birth (prior to diet institution) and daily functioning skills. In contrast to the study hypothesis, there were no significant correlations between daily functioning skills and either current or lifetime phenylalanine levels.