Reliability and the smallest detectable differences of lateral cephalometric measurements.
BACKGROUND
The aim of this study was to determine the reliability and the measuring error (by means of the smallest detectable error) of 11 angular and 4 linear measurements commonly used for cephalometric analysis.


METHODS
Twenty-five digital lateral cephalograms were randomly selected and traced with Viewbox software (version 3.1.1.13, dHAL Software, Kifissia, Greece). This was repeated 3 times by 2 observers during 3 sessions. There was at least 1 week between each session. Differences were analyzed with a repeated measurement analysis of variance (ANOVA). Intraobserver and interobserver reliabilities were calculated with intraclass correlation coefficients (ICC) based on absolute agreement. Measurement error was determined by means of the smallest detectable difference.


RESULTS
The intraobserver agreement of the measurements was good (ICC >0.82). SNA, SNB, ANB, and ANS-Me had the smallest intraobserver errors for both observers (>1.86 mm or degrees). Except for SN-FH (ICC = 0.76), interobserver agreement was good (ICC >0.87).


CONCLUSIONS
Determining the appropriate measuring error of cephalometric measurements by means of the smallest detectable difference is necessary to find the true difference between the start and the end of active treatment. Depending on the magnitude of clinical significance, the measuring error was possibly clinically significant for all variables tested and, therefore, questions the use of these variables to detect the true treatment effect.
Department of Orthodontics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. j.damstra@dmo.umcg.nl
Janalt
J
Damstra
James J R
JJ
Huddleston Slater
Zacharias
Z
Fourie
Yijin
Y
Ren
D000293:Adolescent; D015982:Bias; D001641:Bicuspid / Q000473:pathology; D002508:Cephalometry / Q000706:statistics & numerical data*; D002648:Child; D002680:Chin / Q000473:pathology; D004424:Ear Canal / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D007180:Incisor / Q000473:pathology; D008334:Mandible / Q000473:pathology; D008335:Mandibular Condyle / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008963:Molar / Q000473:pathology; D009295:Nasal Bone / Q000473:pathology; D015588:Observer Variation; D009915:Orbit / Q000473:pathology; D015203:Reproducibility of Results; D012658:Sella Turcica / Q000473:pathology; D012984:Software