Comparison of the General Health Questionnaire and the Hospital Anxiety and Depression Scale.
The specificity and sensitivity of the HAD, 12-item GHQ and CIS were calculated by comparing the scores of dermatological patients on these tests with a criterion measure of disorder. Since psychiatry, along with many other branches of medicine, does not have an error-free criterion, it was assumed that the criterion was an underlying latent construct which was measured by all of the tests and could be derived by factor analysis from the scores on them. No differences were found between the two questionnaires (HAD and GHQ) in their ability to detect cases of minor psychiatric disorder although they were somewhat less reliable than the CIS.