Analyze the role of phenylacetate in the diagnosis of phenylketonuria and its implications for dietary management.

• A. Phenylacetate is a byproduct of tyrosine metabolism, requiring increased tyrosine intake.
• B. Phenylacetate accumulation indicates enzyme deficiency, necessitating a low phenylalanine diet.
• C. Phenylacetate accumulation suggests increased protein intake is necessary.
• D. Phenylacetate is unrelated to phenylalanine metabolism, so no dietary changes are needed.

Answer: (B)