Biometrical Letters Vol. 49(1), 2012, pp. 45-56

Two different medicine measurement methods, which usually do not produce exactly the same results, are used to analyze the serum levels of folic acid in a blood sample. We assess the (dis)agreement of the available data in order to replace the old method (the reference method which involves a lot of human intervention) by the new one (which uses mostly machines), without causing problems in clinical interpretation. The 95% limits of agreement are estimated, before and after a logarithmic transformation, and an appropriate use of regression and a nonparametric approach are also considered. The application of these different statistical techniques are very useful and easily interpreted by medical researchers but, based on the obtained results, we are not confident that the new method can be used in place of the old for clinical purposes.

Measurement methods, graphical techniques, logarithm transformation, regression approach, nonparametric approach.