A Spanish version of the scale is available and its psychometric validity has been established in 175 Spanish subjects with GAD and 45 healthy volunteers (HV) (Bobes et al, 2006). The mean score in the GAD group was 10.6 pre-treatment and 4.4 at six months’ follow-up. Scores varied according to severity of GAD. For those with none, mild, moderate and severe GAD, they were 3.0, 6.6, 10.5 and 11.1.
The scale showed excellent correlations with the Hamilton Anxiety Scale (r = 0.88) and CGI-Severity Scale (r = 0.87). Test-retest reliability was also high (r = 0.89) as was the internal consistency (Kuder-Richardson coefficient = 0.85).
Administration time was 6.5 and 4.5 minutes respectively for the GAD and HV groups.
The cut-point of 4 or greater was found to best differentiate those with and without GAD, at an exceptional degree of accuracy (AUC = 0.971), and sensitivity (0.936), specificity (0.955), PPV of 0.987 and NPV of 0.793.
Bobes and colleagues demonstrated that the Carroll-Davidson GAD scale translation performed well in tracking response to pharmacotherapy in 145 GAD patients. Over the course of 1,3 and 6 months, the score dropped from a baseline of 10.6, to 8.5, 5.6 and 4.4. The effect size of change was 1.6, 3.1 and 3.8.
Reference: Bobes J, Garcia-Calvo C, Prieto R, Garcia-Garcia M, Rico-Demoros F y Grupo Español de Trabajo para la validación de la Escala de Detección del Trastorno de Ansiedad Generalizada según DSM-IV (Escala de TAG de Carroll y Davidson). Psychometric properties of the Spanish version of the Screening Scale for DSM-IV Generalized Anxiety Disorder of Carroll and Davidson. Actas Esp Psiquiatr 2006; 34(2): 83-93.
The following pages on this site provide more information about CDGAD©:
- CDGAD© Main Page
- About the CDGAD© Scale
- User Guide and Interpretation
- Obtaining the CDGAD© Scale
- Frequently Asked Questions (FAQ)
To learn more about GAD, visit the National Institute of Mental Health’s GAD page.