The agreement between two diagnostic methods in binary cases: a proposal.

Abstract

This report can be considered as a resource in the analysis of agreement among raters, clinical tests, observers, judges or experts. The focus is on diagnostic methods. When the true results of diagnostic methods cannot be obtained, studying the agreement between them can reflect the difference between methods. Normal statistical procedures tackling this are not enough for deciding about the agreement from a clinical point of view. The clinical question is whether the new method agrees sufficiently with the old one. In binary cases, a solution for deciding about the agreement from a clinical viewpoint is introduced. The overall agreement is a duality and needs to be studied in two steps. In the first step, a condition for accepting the agreement is proposed: both methods need to have the same nosologic sensitivity and specificity. In the second step, another condition is proposed: the level of the agreement should be greater than a critical value, defined by the clinicians. When both steps show satisfactory results, the new method can replace the old one. The statistical procedures for testing both steps are presented.