Objectives:

1) To determine the diagnostic agreement between five cephalometric indicators of skeletal class and four of facial biotype through Cohen’s weighted kappa test, and 2) to compare these results with those obtained after applying Cohen’s weighted Chi-square test.

Material and methods:

In a sample of 439 lateral teleradiographs, the skeletal class indicators (ANB angle, APDI, FABA angle, Wits indicator, and Beta angle) and facial biotype indicators (FMA, skull base angle, Björk-Jarabak polygon, and VERT index) were determined. Diagnostic concordance between them was assessed using Fleiss’ kappa, Cohen’s weighted kappa, and Cohen’s weighted Chi-square tests.

Results:

Statistically significant differences were observed in both skeletal class and facial biotype diagnoses. While, according to Cohen’s weighted kappa test, most agreements between skeletal class and facial biotype indicators were “Fair” or “Moderate,” Cohen’s weighted Chi-square test revealed highly significant discordance in most comparisons, with negative values in Fleiss’ kappa, indicating a systematic absence of concordance when all indicators were considered simultaneously (Fleiss’ kappaskeletal class = −0.0714, z = −1.46, p = 0.143; Fleiss’ kappafacial biotype = −0.0909, z = −1.28, p = 0.201). The clinical relevance of these findings lies in the fact that diagnosis forms the foundation of proper clinical practice.

Conclusion:

1) When analyzing diagnostic agreement between the five skeletal class indicators and the four facial biotype indicators, significant differences were found between them- a result consistently supported by Cohen’s weighted Chi-square test. 2) Regarding the statistical tests to be used in assessing the significance level of diagnostic agreement, it is recommended to consider: (i) for two evaluators without extreme discrepancies, use the “classical” Cohen’s kappa test; (ii) for two evaluators with extreme discrepancies, use Cohen’s weighted kappa test; and (iii) for more than two evaluators, use Cohen’s weighted Chi-square test.

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