Stability of the ADI-R
criteria. Of the 21 participants not included in the study, 12 did not have ADI-R data both at T1 and
FU, 4 did not meet criteria for autism on the ADI-R at T1 and 5 did not have a confirmed independent
diagnosis of autism/ASD prior to participation in the study. There were no significant differences
between those included in the current study and the 21 children excluded from this sample.
Table 1 describes participant characteristics at T1 and FU. Thirty-two participants were male; 24 were
of white origin, 4 of Black British, 3 of Asian British and 4 of mixed race origin. Twenty-nine had an
independent clinical diagnosis of autism and 6 a diagnosis of ASD.
(Insert Table 1 about here)
Measures
Primary measure- Autism spectrum symptomatology: The Autism Diagnostic Interview- Revised
(ADI-R; Rutter, Le Couteur & Lord, 2003) was used to assess ASD symptomatology. The ADI-R is a
semi-structured interview focusing on three domains: Communication (Verbal- VC and Non Verbal-
NVC), Reciprocal Social Interaction (RSI) and Repetitive Behaviour and Stereotyped Patterns (RBSP).
Each item is scored from 0 (no impairment) to 2/3 (very severe delay/ deviance). In order to meet ADI-
R criteria for autism, a child needs to score above cut-off in all three domains and to present with
developmental concerns prior to the age of 3 years. ADI-R cut-off scores are 10 for RSI, 7 NVC, 8 for
VC and 3 for RBSP. The suggested broader cut off criteria for ASD proposed by Risi et al. (2006) were
employed where participants no longer met the algorithm criteria of the ADI-R at FU. According to
Risi et al. (2006), individuals who meet the criteria for autism on the RSI and on either the NVC/VC
domain or the RBSP domain can be considered to meet ASD criteria on the ADI-R. Only those
children using regular, functional phrase speech were rated on the VC domain (T1 N = 7; FU N=20);
all participants were assessed on the NVC domain at T1 and FU. In order to ensure that scores were