Table 5.

Predicted effect of age, sex and IQ on ASD diagnostic measures in a sub-sample of participants with NVIQ scores

Variable	Chronological age				Intellectual functioning				Sex			Sex by age interaction
	b SE(b)	t	p value	95% CI	b SE(b)	t	p value	95% CI	x 2	p value	d	b SE(b)	t	p value	95% CI
ADI-R—4–5 ever/item scoresa
Social					− .06 (.01)	8.22	< .001	[− .08, − .05]	0.92	.337	.08
Communication					− .02 (.01)	3.17	.002	[− .03, − .01]	0.97	.334	.07
Restricted and repetitive behavioursb					− .01 (.01)	3.49	< .001	[− .01, − .01]	5.07	.024	.21
ADI-R—current item scoresc
Social	− .29 (.05)	5.58	< .001	[-.38, − .19]	− .06 (.01)	7.21	< .001	[− .08, − .04]	2.44	.119	.03	− .13 (.07)	1.80	.071	[− .27, .01]
Communication	− .19 (.04)	5.13	< .001	[− .26, − .12]	− .02 (.01)	3.83	< .001	[− .04, − .01]	0.49	.483	.05	− .07 (.06)	1.26	.206	[− .18, .04]
Restricted and Repetitive Behavioursb	− .01 (.01)	0.02	.981	[− .01, .01]	− .01 (.01)	4.13	< .001	[− .01, − .01]	1.72	.189	.30	− .01 (.01)	0.34	.737	[− .02, .02]
ADOS Calibrated Severity Scoresd
Total	.01 (.02)	0.12	.901	[− .03, .03]	− .03 (.01)	10.2	< .001	[− .04, − .03]	0.62	.430	.19	− .02 (.02)	1.02	.308	[− .07, .02]
Social affect	.01 (.01)	0.70	.486	[− .02, .04]	− .03 (.01)	9.45	< .001	[− .04, − .02]	1.09	.296	.17	− .01 (.02)	0.39	.694	[− .05, .04]
Restricted and repetitive behavioursb	.01 (.01)	0.72	.470	[− .01, .01]	− .01 (.01)	8.33	< .001	[− .01, − .01]	0.11	.739	.19	− .02 (.01)	2.74	.008	[− .03, − .01]

b  regression coefficient, SE(b)  standard error of regression coefficient, t  t-statistic, 95% CI 95% Confidence Interval of regression coefficient

ADI-R Autism Diagnostic Interview—Revised, ADOS Autism Diagnostic Observation Schedule

^a ADI-R 4-to-5 diagnostic/ever scores analyses: N = 1114 participants included

^b log-transformed scores

^c ADI-R current scores analyses: N = 705 participants included

^dADOS analyses: N = 846 participants included