PROPIEDADES PSICOMÉTRICAS DEL PHQ-9 EN USUARIOS PERUANOS CON PROBLEMAS DE CONSUMO DE ALCOHOL DESDE EL MODELO DE RESPUESTA GRADUADA DE SAMEJIMA

Introduction. The PHQ-9 is a scarcely explored instrument from the perspective of item response theory (IRT), particularly in clinical samples with alcohol use problems. Therefore, the aim of the present study is to provide validity evidence for the PHQ-9 based on IRT. Method. A total of 484 individuals with alcohol use problems were selected from the Peruvian national survey (ENDES); 82% were male, and the remaining 17% were female. The study employed a cross-sectional, instrumental design within the framework of IRT, specifically using Samejima’s graded response model. Unidimensionality of the construct was assessed through confirmatory factor analysis, followed by evaluation of model fit indices for a single factor. Additionally, item discrimination and difficulty parameters were examined, along with item and test characteristic curves, among other analyses. Results. The initial factor analysis supported the unidimensionality of the model, which was further confirmed by adequate IRT model fit indices (RMSEA = .062, SRMSR = .068, TLI = .972, CFI = .979). Item 4 (fatigue) showed the highest discrimination, while item 9 (suicidal ideation) exhibited the greatest difficulty. Moreover, the response option “more than half the days” showed a low probability of being selected. Additionally, the depression construct significantly predicted alcohol use (β = 0.24, p < .001). Conclusion. The PHQ-9 is a psychometric instrument suitable for use in clinical populations with alcohol use problems.