Fig. 1.

Bland-Altman plots to identify relative differences between R1 and R2 (panel a); R1 and LC-MS/MS (panel b); and R2 and LC-MS/MS (panel c). Mean differences are represented with solid blue lines, and 95% limits of agreement are represented with dashed lines. Passing-Bablok correlation between the serum levels of cortisol assessed by R2 vs. R1 (panel a); LC-MS/MS vs. R1 (panel b); and LC-MS/MS vs. R2 (panel c). The correlation lines are represented with solid blue lines, and the 95% limits of agreement are represented with dashed lines. The dotted lines indicate lines of identity