Stability of the ADI-R
WPPSI (lower level) (all full scale scores). At T1 the best available test was the WPPSI for one
participant, the Bayley for 17 and the MP for 17 participants. At FU the best available test was the
WISC for 10 participants, the WPPSI (higher) for 6 and the MP for 19 participants.
Adaptive behaviour: Adaptive behaviour was assessed using the Vineland Adaptive Behavior Scales
(VABS, Survey form; Sparrow, Balla &Chicchetti, 1984). Standard and age equivalent scores were
obtained on the Vineland Adaptive Behavior Composite score (VABS ABC) and each of the three
domains (communication, daily living skills, socialization).
Language: Language comprehension was assessed using the British Picture Vocabulary Scales - 2nd
Edition (BPVS; Dunn, Dunn, Whetton & Burley, 1997). Expressive language was assessed using the
Expressive One Word Picture Vocabulary Test (EOWPVT; Gardener, 1990; Brownell, 2000). Since
most children had very limited speech at T1, standard and age equivalent scores on these tests were
highly skewed towards basal and thus raw scores were employed in the analyses reported here.
Reliability: Inter-rater reliability was obtained for 23 assessments (5 WISC, 4 WPPSI, 5 MP, 5 BPVS
and 4 EOWPVT) for 12 randomly selected participants. Video recordings of the assessments were
scored independently by two observers. Intra-class correlation coefficients for total raw scores between
the two observers were very high (r= 1.0, p <.001).
Inter-rater reliability was obtained on ADI-R scores for 6 randomly selected participants (3 verbal, 3
nonverbal). Two examiners, blind to each other’s scores, rated the algorithm items of the ADI-R
independently using detailed written notes made during the interview. Inter-rater reliability for