Sample size determination in method comparison and observer variability studies.

The comparison of two quantitative measuring devices is often performed with the Limits of Agreement proposed by Bland and Altman in their seminal Lancet paper back in 1986. Sample size considerations were rare for such agreement analyses in the past, but recently several proposals have been made depending on how agreement is to be assessed and the number of replicates to be used. We have summarized recent developments and recommendations in various situations including a distinction between method comparison and observer variability studies. These include current state-of-the-art analysis of and reporting guidelines for agreement studies. General recommendations close the paper.