Page 67 - Post-traumatic stress disorder in adults with mild intellectual disability: Screening, assessment, and brief intensive EMDR therapy

Development and evaluation of TS-ID
Cronbach’s alpha for the total symptom frequency score (section two) of
the adult TS-ID version was .94, indicating high internal consistency.
Cut-off value of the Trauma Screener-Intellectual Disability adult version
Because the ROC analyses indicated excellent validity of the TS-ID adult
version in distinguishing individuals with and without a PTSD diagnosis,
a cut-off value was determined for the TS-ID adult version. Based on the
results depicted in Table 1, a cut-off score of 18 for the total symptom
frequency score of the adult TS-ID was the optimal threshold in accordance
with expert consensus, preferring a higher sensitivity at the expense of
specificity. A cut-off score of 18 achieved a sensitivity of 96% and specificity
of 83%, resulting in a Youden’s J index of 0.79, a PPV of 89% and a NPV
of 94%. Thus, sensitivity and specificity were in balance while diagnostic
accuracy was maximal.
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Table 1. Sensitivity, specificity, Youden’s J, PPV and NPV for cut-off scores of the TS-ID adult total
score.
Cutoff score
TS-ID adult
1- Specificity PPV (%) Sensitivity Youden’s J NPV (%)
14 1.00 .71 0.71 82.4 100
15 .98 .78 0.76 85.9 97.0
16 .98 .78 0.76 85.9 97.0
17 .98 .80 0.79 87.3 97.1
18 .96 .83 0.79 88.5 94.4
19 .95 .83 0.78 88.3 91.9
20 .91 .85 0.77 89.5 87.5
21 .82 .88 0.70 90.2 78.3
22 .79 .88 0.66 89.8 75.0
23 .75 .88 0.63 89.4 72.0
24 .71 .93 0.64 93.0 70.4
25 .70 .93 0.62 92.9 69.1
26 .66 .92 0.59 92.5 66.7
27 .63 .95 0.58 94.6 65.0
28 .61 .95 0.56 94.4 63.9
29 .54 .98 0.51 96.8 60.6
30 .50 .98 0.48 96.6 58.8
Note. Bold represents the optimal cutt-off score.
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