Paired comparisons between early treated PKU children and their matched sibling controls on intelligence and school achievement test results at eight years of age

Abstract

Early-treated PKU children were compared to their matched non-PKU sibling controls on Wechsler Intelligence Scale for Children (WISC) and Wide Range Achievement Test (WRAT) results at age 8. Fifty-five PKU children had mean WISC Full Scale IQ score of 100, in comparison to a mean of 107 for their matched sibling controls (p = 0.001). Treatment parameters significantly correlated with sibling-PKU IQ score differences included maximum diagnostic phe level (r = 0.244, p = 0.036) and phe levels at age 6 (r = 0.329, p = 0.007) and at age 8 (r = 0.489, p less than 0.0005). Fifty PKU subjects scored significantly lower than their matched sibling controls on standard scores of the WRAT Reading (102 vs. 107, p = 0.016) and Arithmetic (96 vs, 101, p = 0.006) subtests, and lower, but not significantly so, in Spelling (100 vs. 103, p = 0.145). When the sample was grouped according to diet status at age 8, on-diet PKUs scored at or above the level achieved by their siblings on all three scales of the WISC and all three WRAT subtests, whereas the off-diet group scored from 7 to 13 points below their siblings on all measures. These results suggest that PKU children should restrict phe intake at least through their school years.

A Neuropsychiatric Perspective of Phenylketonuria I: Overview of Phenylketonuria and Its Neuropsychiatric Sequelae

“…They also score slightly lower than their unaffected parents or siblings. 26,27 Cognitive outcomes are significantly correlated inversely to blood Phe levels. During a critical developmental period (age 0 -12 years), each 100 mol/L rise in Phe levels predicted a 1.3-to 3.1-point decline in IQ scores among children treated early with dietary therapy.…”

Phenylketonuria and some aspects of emotional development

“…Early treatment of phenylketonuria (PKU) is highly effective in preserving general intellectual abilities [6,11,19] but many authors have reported neuropsychological/cognitive dysfunction [5,8,9,12,[14][15][16]20]. Little is known about effects of treatment on personality development 9 Aspects of family functioning and emotional development secondary to treatment may add to the problems [2].…”

A test of the frontal‐specificity hypothesis in the cognitive performance of adults with phenylketonuria

“…Studies have shown that, with treatment initiated early, children with PKU attain IQ scores within the normal range, although the scores are often lower than those of non-FKU siblings or parents (Berry, Bofinger, O'Grady, & Perlmutter, 1979;Koch, A;:en, Friedman, & Williamson, 1984;Smith, Beasley, & Ades, 1990). Despite the obvious beneficial effects of a low phe diet, children with PKU have been found to have specific behavioral and cognitive deficits not accounted for by the slightly lower level of intelligence.…”