International assessment of inter- and intrarater reliability of the International Frontal Sinus Anatomy Classification system

Ricardo Villarreal, Bozena B. Wrobel, Luis F. Macias-Valle, Greg E. Davis, Thomas J. Prihoda, Amber U. Luong, K. Christopher McMains, Erik K. Weitzel, William C. Yao, Joe Brunworth, David W. Clark, Salil Nair, Constanza J. Valdés, Ashleigh Halderman, David W. Jang, Rahuram Sivasubramaniam, Zhipeng Zhang, Philip G. Chen

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Background: Inconsistencies in the nomenclature of structures of the frontal sinus have impeded the development of a validated “reference standard” classification system that surgeons can reliably agree upon. The International Frontal Sinus Anatomy Classification (IFAC) system was developed as a consensus document, based on expert opinion, attempting to address this issue. The purposes of this study are to: establish the reliability of the IFAC as a tool for classifying cells in the frontal recess among an international group of rhinologists; and improve communication and teaching of frontal endoscopic sinus surgery (ESS). Methods: Forty-two computed tomography (CT) scans, each with a marked frontal cell, were reviewed by 15 international fellowship-trained rhinologists. Each marked cell was classified into 1 of 7 categories described in the IFAC, on 2 occasions separated by 2 weeks. Inter- and intrarater reliability were evaluated using Light's kappa (κ), the interclass correlation coefficient (ICC), and simple proportion of agreement. Results: Interrater reliability showed pairwise κ values ranging from 0.7248 to 1.0, with a mean of 0.9162 (SD, 0.0537). The ICC was 0.98. Intrarater reliability showed κ values ranging from 0.8613 to 1.0, with a mean of 0.9407 (SD, 0.0376). The within-rater ICC was 0.98. Conclusion: Among a diverse sample of rhinologists (raters), there was substantial to almost perfect agreement between raters, and among individual raters at different timepoints. The IFAC is a reliable tool for classification of cells in the frontal sinus. Further outcome studies are still needed to determine the validity of the IFAC.

Original languageEnglish (US)
Pages (from-to)39-45
Number of pages7
JournalInternational Forum of Allergy and Rhinology
Issue number1
StatePublished - Jan 2019


  • computed tomography
  • endoscopic sinus surgery
  • paranasal sinuses
  • sinus anatomy
  • statistics

ASJC Scopus subject areas

  • Immunology and Allergy
  • Otorhinolaryngology


Dive into the research topics of 'International assessment of inter- and intrarater reliability of the International Frontal Sinus Anatomy Classification system'. Together they form a unique fingerprint.

Cite this