It is important to be aware of the clinically acceptable contractual limits set in advance. As with clinical studies of equivalence or non-inferiority, clinical agreement limits must be set in advance by clinical researchers and biostatistics. Defining these matching limits can be a difficult aspect of the design of comparative studies, as they depend not only on the clinical scenario, but also on other variables. Nevertheless, we must try to define them; a Delphi survey (expert opinion) can be used for the design of the study. This survey is a group facilitation technique, which is a multi-step iterative process designed to transform an opinion into a group consensus . Considering that the LOA confidence interval estimate has a symmetry of μ and μ (μ ≥ 0) and that the size estimates for these two situations should be the same, we only discuss the situation if μ ≥ 0. According to the principle of statistical inference of the Bland-Altman agreements, we can divide total Type I (α) errors into two parts, both of which are α/2. Similarly, we can divide the Type II (β) error into two parts. The first is the first Type II error (No. 1) of the upper LOA limit and the second Type II error (2) of the lower LOA limit (Figure 1).
. Bland indicated the sample size for the study of the concordance between two measurement methods available on its website . In the 1986 launch document, they indicated a 95% confidence interval formula for agreements. The typical error of the 95% chord added to root 3s2/n, where there is the standard deviation between the measurements using the two methods and n the sample size. The confidence interval is the estimate of the limit value, d- plus or minus 1.96s, plus or minus 1.96 standard error, and the sample size can be identified. 8. Bella ML, Teixeira-Pintoc A, McKenzied JE, Oliviere J. A variety of methods: The sample size calculated for two proportions depended on the choice of sample size formula and software. J Clin Epidemiol 2014;67:601-605.
The number of subjects required by Bland`s proposed Bland-Altman method is determined on the basis of the expected width of a confidence interval.