Bland-Altman 1999 Measuring Agreement: Understanding the Basics
Bland-Altman plot is a statistical method that measures the agreement between two quantitative measurements. It is often used to compare the accuracy and precision of two different methods of measuring the same variable. The Bland-Altman plot was introduced by J. Martin Bland and Douglas G. Altman in their 1999 paper titled “Measuring Agreement in Method Comparison Studies.”
In simple terms, the Bland-Altman plot compares two sets of measurements by plotting the difference between the two measurements against their average. The plot helps to identify the systematic bias between the two methods of measurement. It also helps to assess the random variation or measurement error in the two methods.
The Bland-Altman plot is widely used in medical research to compare different measurements of clinical parameters. For example, it can be used to compare two different methods of measuring blood pressure or glucose levels in diabetic patients.
The Bland-Altman plot can be constructed using any statistical software, such as SPSS, SAS, or R. To construct the plot, both sets of measurements are plotted on the y-axis, while the difference between the measurements is plotted on the x-axis. The mean difference is also plotted as a horizontal line on the plot.
The Bland-Altman plot helps to identify any outliers or extreme values that may be present in the data. Outliers can be removed or corrected to improve the accuracy of the comparison.
In conclusion, the Bland-Altman plot is a useful statistical method for measuring agreement between two different methods of measuring the same variable. It helps to identify any systematic bias and measurement error between the two methods. The plot is widely used in medical research to compare different measurements of clinical parameters.