Confirmatory validation of the patient health questionnaire - 4 (PHQ-4) for gastrointestinal disorders: A large-scale cross-sectional survey

Objective: Using the large Rome Foundation Global Epidemiology Survey dataset, the aim of this study was to evaluate the construct and convergent validity and internal consistency of the PHQ-4 across both gastrointestinal and non-gastrointestinal condition cohorts. Another aim was to provide descriptive information about the PHQ-4 including means, confidence intervals and percentage of caseness using a large representative sample. Methods: A cross-sectional survey was conducted in 26 countries. Confirmatory factor and internal consistency analyses were conducted across subsamples of patients with gastrointestinal conditions (i.e., disorders of gut-brain interaction [DGBI; any DGBI, individual DGBI, and DGBI region], gastroesophageal reflux disease (GERD), coeliac disease, diverticulitis, inflammatory bowel disease (IBD), cancer anywhere in the gastrointestinal tract, peptic ulcer) and those without a gastrointestinal condition. Convergent validity was also assessed via a series of Pearson's correlation coefficients with PROMIS (physical and mental quality of life), and PHQ-12 (somatisation). Results: Based on 54,127 participants (50.9% male; mean age 44.34 years) confirmatory factor analysis indicated acceptable to excellent model fits for the PHQ-4 across all subsamples and individual DGBI and DGBI region (Comparative Fit Index >0.950, Tucker-Lewis Index >0.950, Root Mean Squared Error of Approximation <0.05, and Standardised Root Mean Square Residual <0.05). The PHQ-4 was found to demonstrate convergent validity (Pearson's correlation coefficients >±0.4), and good internal consistency (Cronbach's α > 0.75). Conclusions: This study provides evidence that the PHQ-4 is a valid and reliable tool for assessing mental health symptomology in both gastrointestinal and non-gastrointestinal cohorts.