Validity of the 3-item Patient Health Questionnaire (PHQ-3) for Identifying Moderate-to-Severe Depressive Symptoms Among Elderly Perioperative Patients: A Secondary Analysis of a National Prospective Cohort

This is a retrospective observational study based on our hospital's prospective peri-operative elderly patient database. We aim to evaluate the correlation between the 9-item Patient Health Questionnaire (PHQ-9) and the brief 3-item Patient Health Questionnaire (PHQ-3) for screening depressive symptoms among elderly surgical patients. Secondary outcomes include the associations of the two scales with adverse events: 30-day post-operative mortality, readmission, surgical site infection, delirium, and 1-year all-cause mortality. No additional interventions will be performed; only existing routinely-collected clinical data will be analysed.