Comparison of a single self-assessment item with the PHQ-9 for detecting depression in general practice

Background. Several factors need to be considered when selecting a screening tool for depression including accuracy, level of burden for patients and for staff to administer and follow-up. Objective. This study aimed to explore the utility of a single self-assessment item in identifying possible cases of depression in primary care by examining sensitivity and specificity with the nine-item Patient Health Questionnaire (PHQ-9) at different thresholds. Design. Cross-sectional survey presented on a touchscreen computer. Participants. Adult patients attending 12 urban general practices in Australia completed a health status questionnaire (n = 1004). Main measures. Depression was assessed by the PHQ-9 and a single self-assessment item. Sensitivity, specificity, and positive and negative predictive values were calculated for the single item using a PHQ-9 score of 10 or more as the criterion value. Key results. A total of 1004 participants (61% female, 48% aged 55 years or older) completed both the PHQ-9 and a single self-assessment item. When using a threshold of mild depression or greater, the single item had adequate specificity (76%, 95% CI: 71-80%), with 76 out of every 100 people defined as non-depressed by the PHQ-9 also identified as not depressed by the single item. Sensitivity was high (91%, 95% CI: 84-95%), with the single item identifying 91 out of every 100 true cases (as defined by the PHQ-9). Conclusions. The single self-assessment item has high sensitivity and moderate specificity to identify possible cases of depression when used at a threshold of mild depression or greater.