Given a regression equation for method comparison data, here are some simple things can one do, besides the usual. In what follows, Y is defined as the new method and X as the reference method.
If the slope is greater than 1.0 and the intercept greater than 0, Y will never equal X, when X is positive, Y will always be greater.
If the slope is less than 1.0 and the intercept less than 0, Y will never equal X, when X is positive, Y will always be less than X.
If in an Excel file, the slope is in cell A2 and the intercept in cell A3, the point where Y=X is given by the cell formula: = A3/(1-A2).
One can also prepare a table of biases for relevant regions. For example, for a sodium assay,