Table 2. Sensitivity, specificity, positive and negative predictive values, and regression statistics of week two diagnoses to predict week nine traumatic stress diagnoses.

Week two predictor	Week nine outcome	Regression statistics			Positive predictive value	Negative predictive value	Sensitivity	Specificity	% correctly identified
		χ2	p	Odds ratio
DSM-5
ASD	PTSD	28.95	<.0001	26.91	0.48	0.97	0.70	0.92	89.9
- 4+ symptoms	PTSD	28.95	<.0001	15.79	0.30	0.97	0.80	0.80	79.8
‘Two-week PTSD’a	PTSD	36.55	<.0001	22.64	0.41	0.97	0.75	0.88	87.0
Preschool PTSD	Preschool PTSD	39.08	<.0001	26.08	0.39	0.98	0.80	0.87	86.1
DSM-IV
ASD (DSM-IV)	PTSD (DSM-IV)	34.58	<.0001	24.21	0.37	0.98	0.78	0.87	86.5
Either algorithm
ASD	PTSD	35.59	<.0001	21.52	0.39	0.97	0.75	0.88	86.5

Note. Sensitivity = likelihood that someone with a given diagnosis at week nine would have met criteria for the relevant diagnosis at week two. Specificity = likelihood that someone without a given diagnosis at week nine would also not have met criteria for the relevant diagnosis at week two. Positive predictive value = likelihood that someone with a given diagnosis at week two would have the relevant diagnosis at week nine. Negative predictive value = likelihood that someone without a given diagnosis at week two would not have the relevant diagnosis at week nine.

^a‘Two-week PTSD’ this refers to an ‘early PTSD’ algorithm, i.e. ignores the requirement that symptoms be present for at least four weeks.