Validating the bland altman method of agreement
Correlation shows the strength of relation between the devices, but it does not reveal the strength of agreement and is prone to problems.
Relatively simple approaches to reveal agreement are constructing a Bland-Alman plot (also known as Tukey mean difference plot) or similar four-quadrant and polar plots.
High BMI and large baseline waist circumference were associated with a larger degree of underreporting.
Waist circumference measured at the level of the umbilicus was larger than at the natural waist; the mean differences were 0.7 cm (95% CI: 0.4 cm, 1.1 cm) in men and 5.0 cm (95% CI: 4.4 cm, 5.6 cm) in women.
) self-reported circumference at the level of the umbilicus and technician-measured circumference at the natural waist.
At follow-up in the Danish “Diet, Cancer and Health” study, we recruited 176 men and 240 women for a validation study.
Under the theory of statistical inference, the formulae of sample size estimation are derived, which depended on the pre-determined level of , β, the mean and the standard deviation of differences between two measurements, and the predefined limits.
With this new method, the sample sizes are calculated under different parameter settings which occur frequently in method comparison studies, and Monte-Carlo simulation is used to obtain the corresponding powers.
According to the Bland–Altman method, the conclusion on agreement is made based on the width of the confidence interval for LOAs (limits of agreement) in comparison to predefined clinical agreement limit.Bland-Altman plot (Tukey mean-difference plot) is a simple method for analyzing the agreement between two different analysis methods or interobserver variability.Comparison can even be done pixel-by-pixel for parametric images.Prices in € represent the retail prices valid in Germany (unless otherwise indicated). Prices do not include postage and handling if applicable. The Bland–Altman method has been widely used for assessing agreement between two methods of measurement.However, it remains unsolved about sample size estimation.