Abstract WMP89: Examining the Constructs of the Patient Health Questionnaire (PHQ-8) in the Stroke Population

Abstract

Introduction: Most existing screening tools used for post-stroke depression were not originally developed for stroke patients, but the same criteria for identifying depression are usually applied. For instance, the common use of the total score of the Patient Health Questionnaire (PHQ) assumes a unidimentional construct of depression, which may result in distorted performance in the presence of the complexity of stroke. This study aims to test a bifactor measurement model (a depression factor and a stroke-specific factor) using the PHQ-8 in a population-based sample of stroke patients. Methods: The study sample consisted of 613 first-ever stroke patients from the Brain Attack Surveillance in Corpus Christi project (2011-2015). Depressive symptoms at 90 days after stroke were assessed by the PHQ-8. A bifactor measurement model was proposed based on existing knowledge of stroke symptoms, and investigation of depressive symptoms in the study sample. The model included a general depression factor that influences all eight symptoms, and a stroke-specific factor that influences symptoms that frequently overlap between depression and stroke (Figure). The model fit was evaluated using confirmatory factor analysis, and compared with the unidimensional model. Results: The sample was equally distributed by sex, with a mean age of 65.7 (SD=11.0). Fifty-seven percent were Mexican Americans and 38.3% were non-Hispanic Whites. The bifactor model showed statistically significant better fit than the unidimensional model (P<0.001). Conclusion: Future research should explore whether a bifactor measurement model for the PHQ-8, which may result in a different scoring and classification scheme, improves the accuracy of depression screening among stroke survivors.