Table 3. Standardized Estimates of the Reduced A(C)E Bivariate Models of CAST Scores and Each ofthe 4 Clinical Measures of ASD^a.

	Standardized Estimates (95% CI)						Part of Phenotypic Correlation (%)
Measure	h 2	c 2	e 2	r A b	r E b	r ph c	r ph_A d	r ph_E d
CAST	0.78 (0.77-0.79)e	0.00 (0.00-0.00)	0.22 (0.21-0.23)e	NA	NA	NA	NA	NA
DAWBA	0.78 (0.48-0.87)e	0.00 (0.00-0.00)	0.22 (0.13-0.36)e	0.52 (0.47-0.67)e	0.48 (0.32-0.64)e	0.52 (0.48-0.55)e	0.40 (77)e	0.12 (23)e
ADI-R	0.56 (0.37-0.82)e	0.30 (0.08-0.47)e	0.14 (0.07-0.47)e	0.89 (0.70-0.99)e	0.19 (0.00-0.41)	0.61 (0.56-0.66)e	0.58 (≈100)e	0.03 (≈0)
ADOS	0.76 (0.41-0.86)e	0.00 (0.00-0.30)	0.24 (0.14-0.39)e	0.73 (0.63-0.99)e	−0.02 (0.00-0.15)	0.54 (0.51-0.60)e	0.56 (≈100)e	−0.02 (≈0)
Best-estimate diagnosis	0.95 (0.74-0.98)e	0.00 (0.00-0.26)	0.05 (0.02-0.17)e	0.70 (0.63-0.80)e	0.48 (0.16-0.84)e	0.65 (0.24-0.67)e	0.60 (92)e	0.05 (8)e

Abbreviations: See Table 1. c², shared environmental factors estimate; CAST, Covariance of the Childhood Autism Spectrum Test; e², nonshared environmental factors estimate; h², heritability estimate; NA, not applicable.

^aThresholds on the ASD liability were fixed at 5% (broad spectrum) and1% (ASD); the estimates for the CAST score across the 4 models were of similar value and with overlapping 95% CIs.

^bIndicates additive genetic (A) and nonshared environmental (E) correlations between the CAST score and ASD measure.

^cIndicates phenotypic (ph) correlation between the CAST score and ASD measures.

^dIndicates part of the phenotypic correlation due to additive genetic (A) and unique environmental (E) influences (percentage of phenotypic correlation). Proportions cannot be calculated for the ADOS assessment owing to the opposite signs of r_{ph_A} and r_{ph_E}; however, if we disregard the nonsignificant contributions of r_{ph_E} for the CAST-ADOS and CAST-ADI-R relationships, shared genetic effects explain nearly all of the observed correlations.

^eIndicates significant estimates (ie, 95% CIs not spanning 0).