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Assessments for patients with PKU

Early and continuously treated children with PKU risk experiencing learning disabilities and emotional problems.⁷³ Age-appropriate assessments of cognitive, neuropsychological and social-emotional functioning are recommended at various time intervals for patients with PKU:⁷³

• Infancy and preschool years: Annual testing
• Elementary school: Biennial testing preferably by a psychologist familiar with metabolic disorders
• High school and beyond: Psychological evaluations to guide treatment decisions, such as interventions to increase metabolic control or supportive services to alleviate feelings of social isolation.

Measures to assess PKU patients

Non-psychologists might consider administering a set of parent (or self-report) questionnaires when a psychologist is not available to reliably detect deficits in behavior, functioning, and well-being.⁷³ These questionnaires are available in Spanish and English, include forms for infants through adulthood, and can be administered in under an hour. Computerized scoring that provides basic interpretation of the results is also available.⁷³

These questionnaires can be administered every time the child or adult with PKU attends clinic appointments, and can be used to assess changes in functioning that may be related to changes in treatment strategies or blood Phe levels.⁷³ There are no practice effects and the age of the child is taken into consideration because standard scores (not raw scores) are used.⁷³

Age-Appropriate Questionnaires to Assess Patients with PKU⁷³

Psychological Domain	Infants (0-2 years)	Children (3-17 years)	Adults (18 + years)
Adaptive Behavior	ABAS-II	ABAS-II	ABAS-II
Executive Functioning	—	BRIEF	BRIEF
Social/Emotional Functioning	—	BASC-II	BAI & BDI-II

Adaptive behavior

All children and adults should receive the Adaptive Behavior Assessment System-Second Edition (ABAS-II) as a baseline description of their functioning.⁷³ The General Adaptive Composite (GAC) from the ABAS-II correlates reasonably well with IQ. The ABAS-II may be particularly useful for adults, since it includes scales related to the ability to work, live independently and maintain relationships.⁷³

Executive functioning

The Behavior Rating Inventory of Executive Function (BRIEF) provides scores related to executive functioning, including subscales for memory, attention, organization, and planning abilities.⁷³

Social/Emotional functioning

The BASC-II also provides scores related to attention deficit disorders, anxiety, and depression. The Beck Anxiety Inventory (BAI) and Beck Depression Inventory, Second Edition (BDI-II) can be used as self-report measures for adults with PKU or can be completed by an “informant” who knows the individual.⁷³

You may wish to consult with a psychologist for further evaluation if a child is determined by these assessments to be having difficulties.⁷³ Moreover, a physician or psychologist must be consulted if responses indicate that a patient may be at risk for harming him/herself or others.⁷³

Treatments in addition to dietary management

Large Neutral Amino Acids (LNAAs)

LNAAs are a dietary supplement designated for PKU patients:

• Comprised of a mixture of large, neutral amino acids (eg, tyrosine, valine, isoleucine, leucine) that at high concentrations, are believed to inhibit transport of phenylalanine into the brain⁷⁴
• Supplementation is believed to reduce the toxic effects of Phe on the central nervous system⁷⁴
• The supplement is not subject to FDA regulation and there are a scarcity of clinical data suggesting efficacy or safety; clinical trial results remain preliminary^50,75

Drug therapy

In addition to significant adherence issues, arguably, the greatest disadvantage of previous or traditional therapies for elevated Phe arguably lies in the fact that none directly address the underlying defect in the phenylalanine hydroxylase (PAH) enzyme.² Drug therapy may help to improve the body’s natural metabolism of Phe and may act as a chemical chaperone to protect a misfolded enzyme from degradation.^48-50 Learn more

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