TABLE 1.

Characteristics of Infants With Low or High Familial Risk of Autism Spectrum Disorders (ASDs), With and Without ASD Symptoms at 24 Months^a

Characteristic	Low-Risk (N=41)		High-Risk-Negative (N=40)		High-Risk-ASD (N=16)		Analysis of Variance		Pairwise Group Differences
									High-Risk- ASD and Low-Risk	High-Risk-ASD and High-Risk-Negative
							F (df=2, 94)	p	p	p
	N	%	N	%	N	%
Maleb	24	58.5	20	50.0	11	68.8
	Mean	SD	Mean	SD	Mean	SD
Age at initial visit (months)	7.1	0.8	7.0	0.8	7.2	1.0	0.51	0.604	0.636	0.340
Mullen Scales of Early Learningc
Early learning composite score	107.8	10.9	105.0	11.7	101.4	12.7	1.81	0.170	0.066	0.300
Nonverbal developmental quotient	107.4	15.1	106.5	18.5	105.5	11.8	0.08	0.919	0.692	0.833
Verbal developmental quotient	104.2	15.9	97.0	17.4	93.8	19.5	2.79	0.067	0.044	0.535
Visual reception standardized score	53.4	7.6	52.8	8.0	52.6	7.3	0.10	0.904	0.725	0.957
Age at clinical visit (months)	24.8	0.8	25.0	1.1	25.4	1.9	1.57	0.215	0.081	0.200
Autism Diagnostic Observation Scaled
Social affect subscale score	1.9	1.9	2.0	1.4	11.9	4.1	123.0	<0.001	<0.001	<0.001
Repetitive behavior subscale score	0.3	0.7	0.6	0.9	2.6	2.0	25.2	<0.001	<0.001	<0.001
Total score	2.2	2.1	2.6	1.8	14.6	5.5	114.6	<0.001	<0.001	<0.001

^aLow-risk=infants with low familial risk; high-risk-negative=infants with high familial risk who did not meet ASD criteria on the Autism Diagnostic Observation Scale (ADOS) at the 24-month clinical visit; high-risk-ASD=infants with high familial risk who met ASD criteria on the ADOS at the 24-month clinical visit.

^bNo significant difference between groups in sex ratio (Fisher’s exact test).

^cIn the Mullen Scales of Early Learning, the early learning composite score is a composite of the receptive language, expressive language, fine motor, and visual reception standard scores; the nonverbal developmental quotient is the average age equivalent scores for the fine motor and visual reception subscales divided by chronological age multiplied by 100; the verbal developmental quotient is the average age equivalent scores for the receptive language and expressive language subscales divided by chronological age multiplied by 100.

^dThe ADOS was administered when the child was between 23.6 and 32.7 months of age. The ADOS yields a social affect subscale score and a restricted and repetitive behavior subscale score, and the total ADOS score is the sum of the two subscales. All children in the ASD group met diagnostic criteria for a provisional autism spectrum diagnosis according to the ADOS.