Interrater reliability of a phenotypic assessment tool for the ear morphology in microtia

The Elements of Morphology Standard Terminology working group published standardized definitions for external ear morphology. The primary objective of our study was to use these descriptions to evaluate the interrater reliability for specific features associated with microtia. We invited six raters from three different subspecialities to rate 100 ear photographs on 32 features. We calculated overall and within specialty and professional experience intraclass correlation coefficients (ICC) and 95% confidence intervals. A total of 600 possible observations were recorded for each feature. The overall interrater reliability ranged from 0.04 (95% CI: 0.00-0.14) for the width of the antihelix inferior crus to 0.93 (95% CI: 0.91-0.95) for the presence of the inferior crux of the antihelix. The reliability for quantitative characteristics such as length or width of an ear structure was generally lower than the reliability for qualitative characteristics (e.g., presence or absence of an ear structure). Categories with very poor interrater reliability included anti-helix inferior crux width (0.04, 95% CI: 0.00-0.14), crux helix extension (0.17, 95% CI 0.00-0.37), and shape of the incisura (0.14, 95% CI: 0.01-0.27). There were no significant differences in reliability estimates by specialty or professional experience for most variables. Our study showed that it is feasible to systematically characterize many of structures of the ear that are affected in microtia. We incorporated these descriptions into a standardized phenotypic assessment tool (PAT-Microtia) that might be used in multicenter research studies to identify sub-phenotypes for future studies of microtia.