Psychometric properties of the Spanish version of the Patient Health Questionnaire-9 in users of the Ecuadorian public health care system

Introduction: Depression is one of the most prevalent public health problems worldwide and remains an underdiagnosed disease, especially in developing countries. The availability of instruments that permit detecting this problem is essential for reducing the burden of this disorder. The aim of this study was to examine the psychometric properties (factor structure, sex invariance, internal consistency, and convergent and divergent validity) of the Spanish version of the PHQ-9 (Patient Health Questionnaire-9). Method: A sample of 366 public hospital users in Ecuador was recruited and accordingly completed a survey that included sociodemographic data, the PHQ-9, and other standards of measurement such as the Beck Depression Inventory-II (BDI-II), the Generalised Anxiety Disorder Scale (GAD-7), the Positive and Negative Affect Scale (PANAS), and the Quality-of-Life Index (QLI). Results: The unidimensional factor model of the PHQ-9 provided the best fit for the data. The PHQ-9 assesses depressive symptoms equivalently in both sexes, and presents high internal consistency, as well as good convergent and divergent validity with the other constructs. Conclusion: The application of the PHQ-9 could aid in the screening of patients with depressive symptomatology in the Ecuadorian public health system (EPHS).