Table 4.

Concentration of risk of observed post-traumatic stress disorder (PTSD) in the top 5th percentile of predicted PTSD, total sample and stratified by subgroups (n = 378)^a

	Sensitivityb		Positive predictive valuec
	% PTSD	(S.E.)	% PTSD	(S.E.)
Total	44.5	(18.0)	20.4	(9.5)
Age
25+ years	34.0	(13.6)	11.8	(1.3)
<25 years	52.9	(26.3)	32.4	(20.7)
Gender
Male	56.4	(24.3)	29.4	(19.6)
Female	27.9	(23.8)	10.9	(8.8)
Education
High or high-average	50.3	(20.3)	39.5	(16.4)
Low or low-average	22.4	(14.9)	3.9	(0.5)

^aBased on weighted data pooled across the six surveys in high-income countries. See Table note a in Table 2 for a description of the weighting. Ten-fold cross-validation involves dividing the sample into 10 separate random subsamples of equal size, estimating the model in each of the 10 separate 90% subsamples created by deleting one of the 10 subsamples, and applying predicted values based on each set of coefficients only to the remaining 10% of the sample. Replicated cross-validation involves repeating the cross-validation process some number of times (20 times in the current application), with a different random split of the sample into 10 equal-sized subsamples each time. Sensitivity and positive predictive value were calculated separately in each of these 200 subsamples and averaged to produce the results reported here.

^bSensitivity = proportion of all PTSD found among the 5% of respondents with highest predicted probabilities based on the final model.

^cPositive predictive value = prevalence of PTSD among respondents in the row who are among the 5% in the total sample with the highest predicted probabilities based on the final model.