====== 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.