The assessment of generalized anxiety disorder: psychometric validation of the Spanish version of the self-administered GAD-2 scale in daily medical practice

Aim: To psychometrically validate the Spanish version of the self-administered 2-item GAD-2 scale for screening probable patients with generalised anxiety disorder (GAD). Methods: The GAD-2 was self-administered by patients diagnosed with GAD according to DSM-IV criteria and by age- and sex-matched controls who were recruited at random in mental health and primary care centres. Criteria validity was explored using ROC curve analysis, and sensitivity, specificity and positive and negative predictive values were determined for different cut-off values. Concurrent validity was also established using the HAM-A, HADS, and WHODAS II scales. Results: The study sample consisted of 212 subjects (106 patients with GAD) with a mean age of 50.38 years (SD = 16.76). No items of the scale were left blank. Floor and ceiling effects were negligible. No patients with GAD had to be assisted to complete the questionnaire. Reliability (internal consistency) was high; Cronbach's alpha = 0.875. A cut-off point of 3 showed adequate sensitivity (91.5%) and specificity (85.8%), with a statistically significant area under the curve (AUC = 0.937, p < 0.001), to distinguish GAD patients from controls. Concurrent validity was also high and significant with HAM-A (0.806, p < 0.001), HADS (anxiety domain, 0.825, p < 0.001) and WHO-DAS II (0.642, p < 0.001) scales. Conclusion: The Spanish version of the GAD-2 scale has been shown to have appropriate psychometric properties to rapidly detect probable cases of GAD in the Spanish cultural context under routine clinical practice conditions.