The Personal Health Questionnaire: a new screening instrument for detection of ICD-10 depressive disorders in primary care

Background. The next generation of studies on antidepressant drug prescript ions in general practice needs to assess both the patterns of prescription and its appropriateness. This study aimed to assess the performance of the Personal Health Questionnaire (PHQ), a new questionnaire for detecting indi viduals with ICD-10 depressive disorders, to be used in association with co mpanion instruments for assessing the 'quality' of antidepressant prescript ions in primary care settings. Methods. The PHQ was completed by 1413 primary care attenders (100 were re- tested after 7-14 days) and 139 were selected and interviewed using the SCA N-2 and the 17-item HDRS. All data were analysed using appropriately weight ed procedures to control for two-phase sampling design and non-response bia s. Individual weights were estimated by logistic regression analysis and tr imming strategy. Results, PHQ internal consistency and test-retest on both Likert score and number of symptoms were high. The PHQ discriminated well between individual s with and without depressive disorders. A Likert score greater than or equ al to 9 provided a good trade-off between sensitivity (0.78) and specificit y (0.83). The screening accuracy of the PHQ in detecting subjects likely to benefit from antidepressant drug treatment (SCAN cases with a HDRS total s core of 13 or higher) was satisfactory (ROC area 0.87; sensitivity 0.84; sp ecificity 0.78). Conclusions. The PHQ can be strongly suggested as an accurate and economic screener to identify primary care attenders at high risk of being clinicall y depressed. However, in order to identify patients requiring antidepressan t drug treatment, a second-phase assessment of PHQ high scorers (total scor e of greater than or equal to 10), using the HDRS, is needed.