The World Health Organization Composite International Diagnostic Interview (CIDI) is a fully structured diagnostic tool designed for lay interviewers to assess the prevalence of mental and substance use disorders. Earlier versions, such as the CIDI 3.0, demonstrated acceptable individual-level concordance with clinical assessments based on DSM-IV criteria (Haro et al. 2006). The latest iteration (CIDI 5.0) has been updated to operationalize DSM-5 criteria.

Recent evidence from a large-scale, community-based national study in Qatar suggests that under DSM-5 criteria (Khaled et al. 2024), after recalibration, the CIDI 5.0 maintains high specificity (91.9% for MDD, 94.7% for GAD, and 85.5% for PTSD). Sensitivity suggested CIDI diagnoses aligned closely with clinical "gold standard" diagnoses (51.5% for MDD, 50.7% for GAD, and 77.3% for PTSD). Despite the evidence from Qatar, there remains a lack of evidence regarding the validity of the CIDI 5.0 in population-based studies.

Therefore, this study aims to evaluate the diagnostic validity of the CIDI 5.0 for Lifetime MDD, GAD, and PTSD, using the Structured Clinical Interview for DSM-5 (SCID-5) as the definitive clinical gold standard.

Inclusion Criteria:

• All household members aged 18 years old and over are randomly sampled from the Census and Statistics Department List of Quarters
• Live in the address sampled from the Census and Statistics Department List of Quarters
• Reside in Hong Kong for at least six months in the past year
• Able to read and communicate in Chinese or English
• Without linguistic or cognitive difficulties

Exclusion Criteria:

• Domestic workers

This study is a sub-study of the District Health Profile (DHP), which is a district-level representative descriptive cross-sectional study. In DHP, 1% of households in selected Hong Kong districts will be randomly selected from the Census and Statistics Department's list of quarters, with stratification based on districts and housing types; all persons aged 18 and above in the recruited households will be included and surveyed. All individuals will complete the survey for the DHP study, including the CIDI-5 section. Based on prior studies (Haro et al., 2006; Khaled et al., 2024), to ensure adequate statistical power and control for Type I error, the clinical validation study will include 300 individuals. 77 participants will serve as controls with no history of mental disorders, and the remaining sample size will consist of participants with at least one lifetime diagnosis of MDD, GAD, or PTSD, as identified by CIDI-5, aiming to reach at least 112 samples for each diagnosis.