Follow-up at mid-school age (9-13 years) of children assessed for autism spectrum disorder before the age of four.

Background: Studies of diagnosis and outcome in mid-school age children (9-13 years) referred early in life for a suspected autism spectrum disorder (ASD) are scarce.

Aims: This study aimed to describe outcome, developmental change and the stability of the early diagnosis in mid-school age.

Methods: Children consecutively referred to a specialized autism unit at a regional psychiatric diagnostic centre in Denmark before the age of 4 were contacted in mid-school age (9-13 years). 14 children with ASD and 9 children diagnosed outside the spectrum were included. Current clinical diagnosis, autism characteristics, intellectual abilities and adaptive functioning were assessed at follow-up, and investigated in relation to early measures of intellectual abilities and difficulties in social and communicative situations.

Results: The stability of an early ASD diagnosis was confirmed. However, a high degree of change into the autism spectrum was found for children who were initially diagnosed with another developmental disorder. A positive change with regard to IQ level was evident at the individual level. At group level, there was a tendency for lower functioning in the children diagnosed early with ASD. Early measures of intellectual abilities, and of social and communicative difficulties, predicted between 16% and 50% of the variance in intellectual abilities and adaptive functioning.

Conclusions: The findings are in line with follow-up studies in preschool and early school age but highlight the need to monitor early diagnostic decisions, and the need for more nuanced baseline and outcome measures that may help increase our prognostic understanding.