The origins, effects, and treatment of PKU have been discussed previously. The following article focuses on the effects PKU has on executive functioning specifically. To ascertain these effects the implementation of the Behavior Rating Inventory of Executive Functioning (BRIEF) is proposed. This is an easily applied standardized questionnaire which can also be employed by non-psychologists. However, the accuracy of the BRIEF has been called in to question. To address this, the authors also use the Amsterdam Neuropsychological Tasks (ANT) measure, which has been used several times in the past to ascertain the neurocognitive functioning of PKU patients of various ages and early and continued treatment. Using the two tests, the authors attempt to investigate whether the BRIEF-A (adult version) is a useful instrument in the screening of patients with PKU during their daily living.
The sample for this study consisted of 55 Dutch adult patients with PKU. Additionally, this study was a part of the PKU-COBESO mentioned in the previous article. The BRIEF-A test consisted of 75 questions 9 subdomains related to executive functioning, 4 subdomains which determine the Behavioral Regulation Index (BRI). The overall executive functioning in daily life score is denoted as the Global Executive Composite (GEC).
For the ANT, three tests were used to measure executive functioning: Shifting Attentional Set Visual (SSV), Sustained Attention Dots (SAD), and Feature Identification (FI).
Of the 55 patients, 23 scored within the borderline/clinical range of the BRIEF-A. Patients showed problems in the domains of cognitive flexibility and inhibitory control when compared to the healthy population. Subsequently, two groups were formed on the basis of BRIEF-A GEC scores using a cutoff T-score of >= 60 (>1 SD above the mean). No significant differences were found between the groups on the basis of gender, age, and IQ. Additionally, no significant differences were found between the two groups on concurrent and historical Phe concentration levels. There was found to be some agreement between the BRIEF and the ANT indicating that the null hypothesis could not be rejected.
The fact that patients with PKU still face problems in attention and learning was the driving factor for this investigation into the efficacy of the BRIEF as a tool for monitoring patients. The results show that 42% of patients scored in the borderline/clinical range. Despite this, only 11% of patients showed scores greater than 1 SD. From the results of the ANT, we see that PKU patients had problems with inhibitory control and cognitive flexibility. The BRIEF-A appears to identify executive dysfunction across studies.
