What is Known: •A prior study found that 29 % of children with FDD scored positive on ASD screening questionnaires. •Whether positive screens correctly identify ASD in children with FDD is unknown.

What is New: •This study shows that positive ASD screens do not correctly identify ASD in children with FDD. However, the use of ASD screening questionnaires can identify previously unrecognized and untreated behavioral/developmental disorders in children with FDD. •High screening scores are more common in children with FC with FI and in children with poorer responses to current medical treatments.