Validity of the Patient Health Questionnaire-9 in assessing major depressive disorder during inpatient spinal cord injury rehabilitation

Abstract

Objective: To investigate the validity of the Patient Health Questionnaire-9 (PHQ-9) depression screening measure in people undergoing acute inpatient rehabilitation for spinal cord injury (SCI).

Design: We performed a blinded comparison of the PHQ-9 administered by research staff with the major depression module of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID) conducted by a mental health professional.

Setting: Inpatient rehabilitation units.

Participants: Participants (N=142) were patients undergoing acute rehabilitation for traumatic SCI who were at least 18 years of age, English speakers, and without severe cognitive, motor speech, or psychotic disorders. We obtained the SCID on 173 (84%) of 204 eligible patients. The final sample of 142 patients (69%) consisted of those who underwent both assessments within 7 days of each other.

Interventions: Not applicable.

Main outcome measures: PHQ-9 and SCID major depression module.

Results: Participants were on average 42.2 years of age, 78.2% men, and 81.7% white, and 66.9% had cervical injuries. The optimal PHQ-9 cutoff (≥11) resulted in 35 positive screens (24.6%). Key indices of criterion validity were as follows: sensitivity, 1.00 (95% confidence interval [CI], .73-1.00); specificity, .84 (95% CI, .76-.89); Youden Index, .84; positive predictive value, .40 (95% CI, .24-.58); and negative predictive value, 1.00 (95% CI, .96-1.00). The area under the receiver operator curve was .92, and κ was .50. Total PHQ-9 scores were inversely correlated with subjective health state and quality of life since SCI.

Conclusions: The PHQ-9 meets criteria for good diagnostic accuracy compared with a structured diagnostic assessment for major depressive disorder even in the context of inpatient rehabilitation for acute traumatic SCI.