Accuracy and reliability of the expected root position: Methodological issues to avoid misinterpretation

Abstract

We read a recently published study by Lee et al in the October, 2019, issue of the Journal (Lee RJ, Ko J, Park J, Pi S, Devgon D, Nelson G, et al. Accuracy and reliability of the expected root position setup on clinical decision making of root position at midtreatment. Am J Orthod Dentofacial Orthop 2019;156:566-73). The authors aimed to study the accuracy and reliability of clinical decisions made on root position using the expected root position (ERP) setup. Four examiners assessed both the cone-beam computed tomography (CBCT) scan and ERP setup and made clinical decisions regarding the root position with each method. Cohen's kappa was determined to assess intraoperator and intermethod reliability. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated to determine the accuracy of the ERP setup. They showed that the kappa values for intraoperator reliability for both the CBCT scan and ERP setup fell within the 0.61-0.80 range. The kappa values for intermethod reliability between the CBCT scan and ERP setup fell within the 0.61-0.80 range for all tooth groups. Although this article has provided valuable information, reconsidering some substantial points might help the clarity of the method and an accurate interpretation of the study.1Szklo M. Nieto F.J. Epidemiology: beyond the basics. Jones & Bartlett Publishers, Burlington2014Google Scholar,2Sabour S. A common mistake in assessing the diagnostic value of a test: failure to account for statistical and methodologic issues.J Nucl Med. 2017; 58: 1182-1183Crossref PubMed Scopus (35) Google Scholar Regarding reliability, for qualitative variables with more than 2 categories, using simple kappa is a common mistake because kappa has its own limitations. First, it depends on the prevalence in each category. Second, it also depends on the number of categories. Finally, the physician's opinion and the patient's clinical status should not be neglected. The weighted kappa is a more appropriate statistical test and should have been used to assess the reliability in this paper. For assessing reliability for a qualitative variable, relying on the kappa coefficient can lead to a misleading message. Accuracy and reliability of the expected root position setup on clinical decision making of root position at midtreatmentAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 156Issue 4PreviewAccurate root position is imperative for successful orthodontic treatment that is stable and functional. Current methods to monitor root position are either inaccurate or use relatively high levels of radiation. A method to generate an expected root position (ERP) setup has been reported to have the potential to accurately evaluate root position with minimal radiation. The purpose of this study was to determine the accuracy and reliability of the clinical decisions made on root position using the ERP setup. Full-Text PDF Authors’ responseAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 157Issue 2PreviewWe thank our colleagues very much for their interest in our article. We appreciate their insights because they increase understanding within our community on statistical analysis and improve our clinical studies going forward. In addition, we are grateful for their explanation on kappa statistics and their suggestion of using a weighted kappa statistical test. Full-Text PDF