Psychometric Properties of the Patient Health Questionnaire-9 in Patients With Heart Failure and an Implantable Cardioverter Defibrillator

BACKGROUND: Depressive symptoms are prevalent in patients with heart failure (HF) and an implantable cardioverter defibrillator (ICD), and are commonly undiagnosed and negatively affect patients' health. Therefore, finding a valid and reliable instrument to measure depressive symptoms in this population is crucial. OBJECTIVE: The aim of the study was to evaluate the psychometric properties of the Patient Health Questionnaire-9 (PHQ-9) in this population. METHODS: We conducted a secondary analysis of data from 258 patients with HF and an ICD. Internal consistency reliability was assessed using Cronbach's alpha and item analysis. Construct validity was assessed using hypothesis testing and convergent validity tests. The exploratory factor analysis was used to determine the dimensionality of the PHQ-9. RESULTS: The PHQ-9's internal consistency reliability was supported by a Cronbach's alpha of 0.85. The inter-item correlations ranged from 0.22 to 0.56. Our hypotheses that patients with moderate/severe HF symptoms would have higher PHQ-9 scores than those with no/mild symptoms (9.2 ± 6.2 vs. 5.0 ± 5.1; t = -5.9, P < .001), and that patients with higher anxiety would have higher depressive symptoms than those without anxiety (9.7 ± 6.0 vs. 4.3 ± 4.8; t = -8.0, P < .001) were supported. A significant correlation was found between the PHQ-9 and the Minnesota Living with Heart Failure (r = 0.73, P < .001), supporting convergent validity. The exploratory factor analysis results revealed that the PHQ-9, as expected, had 1 dimension explaining 47.29% of the variance of depressive symptoms. CONCLUSIONS: Our findings provide evidence supporting the reliability and validity of the PHQ-9 as a measure of depressive symptoms in patients with HF and an ICD.