Rationale of New Grading System: Central Compartment Atopic Disease

Central compartment atopic disease (CCAD) has recently been recognized as a distinct phenotype within the spectrum of type 2-dominant chronic rhinosinusitis (CRS). Although international guidelines highlight polypoid changes in the central nasal cavity, standardized diagnostic and classification criteria are still lacking. This study aims to develop and internally validate a consensus-based classification system through expert agreement.

A two-round modified Delphi study was conducted with 10 international rhinology experts. Participants evaluated the need for a specific grading framework, the relative diagnostic value of nasal endoscopy versus radiology, and the clarity and applicability of the proposed criteria (Grades 0-IV). Six representative endoscopic and radiologic cases were used in each round to assess interpretive accuracy and interobserver agreement. Consensus was predefined as ≥ 80% of ratings in the top two categories (4-5) on a 5-point Likert scale.

Eighty percent of experts identified nasal endoscopy as the primary diagnostic tool in the first Delphi round. The interpretive accuracy of the preliminary grading system was high, with all panelists correctly recognizing the proposed distinctions. Interobserver agreement was substantial (κ = 0.72). In the second round, refined definitions improved overall consensus and reproducibility. Endoscopy was reaffirmed as the cornerstone of diagnosis, while radiology played a complementary role. Diagnostic clarity and agreement increased, reaching κ = 0.80.

The consensus process confirmed nasal endoscopy as the key diagnostic method for CCAD, supported by substantial interobserver reproducibility. The refined definitions improved clarity and agreement, facilitating differentiation from other CRS phenotypes and establishing a reliable framework for future research.