(PS2-39) Measurement Invariance and Differential Item Functioning of the PHQ-9 Between Spanish and English Speakers in Emergency Department Settings

Background:   The Patient Health Questionnaire-9 (PHQ-9) is a self-administered screening tool for depression that has gained popularity in research, primary care, and hospital settings (Kroenke et al., 2001). The PHQ-9 has been translated into Spanish; however, little is known about the measurement invariance between Spanish-speakers and English-speakers. Understanding how Spanish-speaking populations self-report mental health symptoms can help improve accuracy of detecting and treating depression. This is especially important as Spanish-speaking individuals are often a part of an ethnic minority group with historic and structural barriers that interfere with receiving culturally responsive mental health care. 

Methods:   Adult patients (aged 25 and older) were admitted to emergency departments in a southeastern state for medical care. As part of routine screening, nursing staff administered the PHQ-9, either in English (n = 6253) or in Spanish (n = 907) at intake. Confirmatory factor analysis (CFA) was performed to establish a two-factor model, consisting of a cognitive/affective factor and a somatic factor, to test for measurement invariance between language groups. Multi-group CFA tested configural, metric, and scalar invariance. Ordinal logistic regression (OLR) and item response theory (IRT) analyses were conducted to determine the differential item functioning (DIF) between language groups.  

 

Results: Multi-group CFA analysis confirmed configural invariance (CFI = 0.934, TLI = 0.909, RMSEA = 0.072, SRMR = 0.043), but showed mixed support for metric and scalar invariance (Metric: CFI = 0.931, TLI = 0.916, RMSEA = 0.137, SRMR = 0.045; Scalar: CFI = 0.923, TLI = 0.916, RMSEA = 0.102, SRMR = 0.054). OLR analysis found that Spanish-speaking participants had a higher mean level of depression (0.44 standard deviations above English-speaking participants). Although IRT DIF analysis shows statistically significant differences in response patterns for all items between groups (p< 0.001), McFadden’s pseudo-R² values (all< 0.03) indicate these values are not clinically significant.

Conclusions: OLR and IRT findings provide insight into how Spanish-speaking patients respond to each item of the PHQ-9. Understanding these differences can help clinicians better diagnose and treat depressive symptoms as they present in Spanish-speaking populations. Despite these differences, McFadden’s pseudo-R² values are low, supporting the validity and clinical utility of the Spanish PHQ-9. These findings support the use of the Spanish PHQ-9 to screen for depression in Spanish-speaking populations in emergency department settings, contributing to more culturally and structurally competent mental health care while emphasizing the importance of linguistic and cultural differences.