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.