Interobserver agreement of the anatomic and physiological classification system for adult congenital heart disease

The Anatomic and Physiological (AP) classification system proposed in the 2018 American College of Cardiology/American Heart Association adult congenital heart disease (ACHD) guidelines assigns 2 dimensions to each patient: anatomic class (AnatC) and physiological stage (PhyS). This approach has not been tested in practice; we assessed interrater reliability and identified sources of disagreement.

Consensus definitions for AP categories were developed with input from 4 experts. Research assistants (RAs) assigned AnatC/PhyS for patients in the Boston ACHD Biobank, a prospectively enrolled cohort of ambulatory ACHD patients ≥18 years old seen between 2012 and 2019. Two (of 4) expert reviewers then independently assigned AnatC/PhyS for 41 patients. Interrater reliability was assessed with linearly weighted kappa (κ_ω) for agreement between (1) experts and (2) an RA and an expert. Experts examined disagreements and identified sources of variability and areas requiring clarification.

Interexpert agreement for AnatC was excellent, with agreement on 38/41 (92.7%) cases and κ_ω 0.88 [0.75, 1.01]. Agreement for PhyS was less robust, with consensus on 24/41 cases (59.5%), κ_ω 0.57 [0.39, 0.75]. Expert-RA agreement was lower for AnatC (κ_ω 0.77 [0.60, 0.95]), whereas PhyS was similar to interexpert agreement (κ_ω 0.53 [0.34, 0.72]). There was ambiguity in the definitions of (1) arrhythmia status, (2) cyanotic CHD, and (3) valve disease.

Although AnatC can be assessed reliably, that is not true for the PhyS part of the AP classification proposed in the 2018 American College of Cardiology/American Heart Association guidelines. Reliability of PhyS would be strengthened by more precise definitions readily interpretable in clinical practice.