Agreement among international periodontal experts using the 2017 World Workshop classification of periodontitis

Background A new periodontitis classification was recently introduced involving multidimensional staging and grading. The aim of the study was to assess if individuals well-trained in periodontics consistently used the new classification for patients with severe periodontitis. The secondary goal was to identify "gray zones" related to classifications. Methods Participants (raters) individually classified 10 pre-selected severe periodontitis cases using the 2017 World Workshop classification. An internet case-based study was conducted after inviting members from American Academy of Periodontology and European Federation of Periodontology. Gold-standard diagnoses were determined by five experts who developed the new periodontitis classification. Inter-reliability agreement among raters was assessed using Fleiss Kappa index with the jackknife method for linearly weighted kappa calculations. McNemar test was used to determine symmetry between raters and gold-standard panel. Results A total of 103 raters participated and classified nine clinical cases. Fleiss Kappa values showed moderate inter-examiner consistency among raters for stage (K value: 0.49; 95% CI, 0.19 to 0.79), grade (K value: 0.50; 95% CI, 0.30 to 0.70) and extent (K value: 0.51; 95% CI, 0.23 to 0.77). When analyzed as composite (stage, grade, extent) a moderate inter-reliability was present among raters, k = 0.479 (K value: 0.47; 95% CI, 0.442 to 0.515). Agreement between raters and gold-standard panel was staging 76.6%; grading 82%; and extent 84.8%. In six of nine cases 77% to 99% of raters consistently agreed with gold-standard panel, and the other three cases had gray zone factors that reduced rater consistency. Conclusions Clinicians trained in the 2017 World Workshop periodontitis classification demonstrated moderate concordance in classifying nine severe periodontitis cases, and in six of nine cases raters consistently agreed with the gold-standard panel.