Reliability and validity of the Dutch version of the Glasgow Anxiety Scale for people with an Intellectual Disability (GAS-ID)
Article first published online: 10 OCT 2012
© 2012 The Authors. Journal of Intellectual Disability Research © 2012 John Wiley & Sons Ltd, MENCAP & IASSID
Journal of Intellectual Disability Research
Volume 57, Issue 8, pages 728–736, August 2013
How to Cite
Hermans, H., Wieland, J., Jelluma, N., Van der Pas, F. and Evenhuis, H. (2013), Reliability and validity of the Dutch version of the Glasgow Anxiety Scale for people with an Intellectual Disability (GAS-ID). Journal of Intellectual Disability Research, 57: 728–736. doi: 10.1111/j.1365-2788.2012.01632.x
- Issue published online: 19 JUN 2013
- Article first published online: 10 OCT 2012
- Manuscript Accepted: 30 AUG 2012
- Netherlands Organisation for Health Research and Development. Grant Number: 57000003
- mental health;
In the Netherlands, no self-report screening questionnaire for anxiety in people with intellectual disabilities (ID) was available yet. Therefore, we have translated the Glasgow Anxiety Scale for people with an Intellectual Disability (GAS-ID) into Dutch and studied its reliability and validity in adults with borderline, mild or moderate ID.
Test–retest reliability was studied in 66 participants, convergent validity against the Anxiety sub-scale of the Hospital, Anxiety and Depression Scale (HADS-A) in 96, and criterion validity against psychiatric diagnosis in 195 participants.
Internal consistency was α = 0.86 and test–retest reliability ICC = 0.89 (95% CI: 0.82–0.93). Correlation with the HADS-A was r = 0.61 (95% CI: 0.47–0.72); sensitivity was 83.9% (95% CI: 72.2–91.2) and specificity was 51.8% (95% CI: 43.6–59.9) using a cut-off score of 17. Missed diagnoses (false-negatives) were mostly specific phobias. Of the false-positives, 38 of 66 participants (58%) had another psychiatric diagnosis.
The Dutch version of the GAS-ID is a reliable screening instrument with satisfactory sensitivity, but moderate specificity for anxiety disorders. Although specificity for anxiety disorders is only moderate, high scores appear to be indicative of other psychiatric problems too, justifying referral for psychiatric assessment of false-positives.