Table 4.

ROC Analyses

	Age (in months)	Area Under Curve	Standard Error	Optimal Thresholda	Youden Index	Sensitivity	Specificity	Positive Predictive Value	Negative Predictive Value	Risk Ratio
Autism/ASD vs. other delays	6	.68	0.12	2	0.33	0.33	1.00	1.00	0.74	3.83
	12	.74**	0.08	1	0.42	0.82	0.60	0.58	0.83	3.50
	18	.71*	0.08	2	0.34	0.57	0.77	0.60	0.75	2.40
(Autism/ASD + other delays) vs. low-risk typical	6	.47	0.08	2	0.01	0.12	0.89	0.43	0.58	1.02
	12	.61	0.06	1	0.21	0.57	0.64	0.51	0.69	1.65
	18	.67***	0.05	2	0.27	0.36	0.92	0.77	0.64	2.16

ASD, autism spectrum disorders.

^aThreshold based on Youden's index³⁶ (max [sensitivity_I + Specificity_i − 1]).

^*p < .05.

^**p < .01.

^***p < .001.