Unfolding the phenomenon of interrater agreement: a multicomponent approach for in-depth examination was proposed

Objective: The overall objective was to unfold the phenomenon of interrater agreement: to identify potential sources of variation in agreement data and to explore how they can be statistically accounted for. The ultimate aim was to propose recommendations for in-depth examination of agreement to improve the reliability of assessment instruments. Study Design and Setting: Using a sample where 10 rater pairs had assessed the presence/absence of 188 environmental barriers by a systematic rating form, a raters x items data set was generated (N = 1,880). In addition to common agreement indices, relative shares of agreement variation were calculated. Multilevel regression analysis was carried out, using rater and item characteristics as predictors of agreement variation. Results: Following a conceptual decomposition, the agreement variation was statistically disentangled into relative shares. The raters accounted for 6-11%, the items for 32-33%, and the residual for 57-60% of the variation. Multilevel regression analysis showed barrier prevalence and raters' familiarity with using standardized instruments to have the strongest impact on agreement. Conclusion: Supported by a conceptual analysis, we propose an approach of in-depth examination of agreement variation, as a strategy for increasing the level of interrater agreement. By identifying and limiting the most important sources of disagreement, instrument reliability can be improved ultimately. (C) 2012 Elsevier Inc. All rights reserved.