Diagnostic Accuracy of the Japanese Version of the GAD-2 for Screening Generalized Anxiety Disorder in Primary Care

Abstract

Objective
To evaluate the diagnostic performance of the Japanese version of the Generalized Anxiety Disorder 2-item scale (J-GAD-2) as an ultra-brief screening instrument for detecting generalized anxiety disorder (GAD) in primary care settings.

Methods
This study is a secondary analysis of data from a previously conducted validation study of the Japanese version of the GAD-7 (J-GAD-7). In the original study, participants completed the J-GAD-7 questionnaire and subsequently underwent a structured diagnostic interview using the Mini-International Neuropsychiatric Interview (MINI-Plus). The first two items of the J-GAD-7 were used to derive the J-GAD-2.
Diagnostic accuracy was evaluated using receiver operating characteristic (ROC) analysis, sensitivity, specificity, positive likelihood ratios, and stratum-specific likelihood ratios (SSLRs). Construct validity was examined using the Mental Component Summary (MCS) score of the Short Form-8 Health Survey (SF-8).

Results
ROC analysis demonstrated excellent discrimination ability of the J-GAD-2 (AUC = 0.902). The optimal cut-off value was >=3, which displayed sensitivity of 82.3%, specificity of 81.2%, and a positive likelihood ratio of 4.6 (95% CI: 3.0-7.1). The SSLRs of the J-GAD-2 scores of 0-2, 3-4, and 5-6 for GAD were 0.23 (95% CI: 0.14-0.37), 2.48 (95% CI: 1.41-4.38), and 14.38 (95% CI: 4.9-41.51), respectively. Findings of the Mann-Whitney U test showed a significant relationship between the severity of the J-GAD-2 and the SF-8 MCS score (U=882.5, Z=-7.234, P <.001). These findings indicate that the J-GAD-2 provides clinically meaningful stratification of GAD risk in primary care populations.

Conclusions
The J-GAD-2 is a brief, clinically useful screening instrument for detecting GAD in primary care settings. Its brevity makes it suitable for routine screening in busy clinical environments.