title: Concordance analysis: part 16 of a series on evaluation of scientific publications.
abstract: BACKGROUND
  In this article, we describe qualitative and quantitative methods for assessing the degree of agreement (concordance) between two measuring or rating techniques. An assessment of concordance is particularly important when a new measuring technique is introduced.
  
  
  METHODS
  We give an example to illustrate a number of simple methods of comparing different measuring or rating techniques, and we explain the underlying principle of each method. We also give further illustrative examples from medical research papers that were retrieved by a selective literature search.
  
  
  RESULTS
  Methods of comparing different measuring or rating techniques are of two kinds: those with a nominal rating scale and those with a continuous rating scale. We only discuss methods for comparing one measuring or rating technique with another one. Moreover, we point out some common erroneous approaches to concordance analysis.
  
  
  CONCLUSIONS
  Concordance analysis is needed to establish the validity of a new diagnostic measuring or rating technique or to demonstrate the near-equivalence of multiple measuring or rating techniques. Erroneous approaches to concordance analysis can lead to false conclusions.
authors: Institut für Biometrie und Klinische Forschung (IBKF) Westfählische Wilhelms-Universität Münster Albert-Schweitzer-Campus, Germany. robert.kwiecien@ukmuenster.de
authors: Robert
authors: R
authors: Kwiecien
authors: Annette
authors: A
authors: Kopp-Schneider
authors: Maria
authors: M
authors: Blettner
mesh_terms: D003196:Computer Graphics; D016001:Confidence Intervals; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005069:Evaluation Studies as Topic; D006801:Humans; D008432:Mathematical Computing; D015588:Observer Variation; D011237:Predictive Value of Tests; D011643:Publishing / Q000706:statistics & numerical data*; D012015:Reference Standards