Abstract
There is an issue of validation that is important even for clinical practice. Probably most important is assessment of agreement against gold standard in a validation study.
Validation study is to be carried out on target population, and the range of measured values should be comparable to the range in target population. Otherwise the usefulness and extrapolation of the results of validation study is limited.
The crucial thing is the methodology and interpretation. Simple correlation analysis and comparison of arithmetic means seem to be inappropriate.
As the most useful there is difference graph after Bland and Altman with subsequent calculation of 95% limits of agreement.Weprefer this method to other methods like typical error for its clarity and simplicity.