RESUMEN
Abstract The ADHD Rating Scale (ADHD RS-IV; parent report) and Adult ADHD Self-Rating Scale (ASRS; self-report) are validated instruments for measuring symptoms of attention-deficit/hyperactivity disorder (ADHD). The objectives of this study were to elicit descriptions of phenylketonuria (PKU) symptoms and assess content validity of these instruments in PKU. Parents (N = 15) of children with PKU (?8 years old) and adults with PKU (N=13) described PKU-related symptoms and commented on the scale's clarity, comprehensiveness, and relevance to their experience with PKU. Most of the adults (84.6%) and all of the children were on a phenylalanine-restricted diet, according to respondent report. The inattentiveness symptoms reported by participants mapped to the inattentive items of the questionnaires. Most participants felt the inattentive items were clear and relevant to their experience. Despite study design limitations, these results demonstrate the relevance of assessing inattentiveness in PKU, and both instruments achieved content validity for inattentive subscale items.