Concordance Study
Definition: A *concordance study* evaluates the degree of agreement between two or more observers, diagnostic tools, or treatment decisions when applied to the same cases or data.
Key Features
- Objective: Assess consistency between different evaluators or systems.
- Metrics commonly used:
- Cohen’s kappa or Fleiss' kappa (for categorical variables)
- Intraclass Correlation Coefficient (ICC) (for continuous variables)
- Bland-Altman plots
- Percentage agreement
- Typical design: Cross-sectional or retrospective analysis using shared clinical data or case vignettes.
Applications
- Inter-rater reliability (e.g., between radiologists)
- Comparing diagnostic or management decisions across clinical specialties
- Assessing guideline adherence across practitioners
Example (Neurosurgery)
A concordance study may analyze how often neurosurgeons and chiropractors agree on diagnosis and management of patients with low back pain, measuring the rate of agreement across a shared set of patient cases.