The Bland-Altman analysis is a statistical method used to assess the agreement between two quantitative measurement methods. It was introduced by Altman and Bland in 1983 and is widely used in clinical laboratory research to evaluate the consistency of results from different methods. Unlike correlation and regression, which focus on the relationship between variables, Bland-Altman analysis quantifies the mean difference between the two methods and constructs limits of agreement, which define the range within which 95% of the differences between the two methods fall. The Bland-Altman plot is a scatter plot where the Y-axis represents the difference between the two measurements, and the X-axis represents the average of the two measurements. The plot helps identify any systematic bias (a constant difference between the methods) and assess the variability of the differences. The limits of agreement are calculated using the mean difference and the standard deviation of the differences. These limits indicate the range within which most differences between the two methods are expected to fall. The Bland-Altman method is particularly useful when comparing methods that are not necessarily reference methods. It allows for the evaluation of agreement at different magnitudes of the measured variable. However, it does not determine whether the agreement is acceptable or not; acceptable limits must be defined a priori based on clinical, biological, or other relevant criteria. The Bland-Altman plot can also be used to express differences as percentages of the mean value, which is useful when the variability of differences increases with the magnitude of the measurement. This approach helps in assessing agreement relative to the true value. In addition to the Bland-Altman plot, other statistical methods such as correlation and regression are often used in method comparison studies. However, these methods are not suitable for assessing agreement between methods, as they focus on the relationship between variables rather than the differences between them. The Bland-Altman method provides a more accurate and comprehensive assessment of agreement between two measurement methods.The Bland-Altman analysis is a statistical method used to assess the agreement between two quantitative measurement methods. It was introduced by Altman and Bland in 1983 and is widely used in clinical laboratory research to evaluate the consistency of results from different methods. Unlike correlation and regression, which focus on the relationship between variables, Bland-Altman analysis quantifies the mean difference between the two methods and constructs limits of agreement, which define the range within which 95% of the differences between the two methods fall. The Bland-Altman plot is a scatter plot where the Y-axis represents the difference between the two measurements, and the X-axis represents the average of the two measurements. The plot helps identify any systematic bias (a constant difference between the methods) and assess the variability of the differences. The limits of agreement are calculated using the mean difference and the standard deviation of the differences. These limits indicate the range within which most differences between the two methods are expected to fall. The Bland-Altman method is particularly useful when comparing methods that are not necessarily reference methods. It allows for the evaluation of agreement at different magnitudes of the measured variable. However, it does not determine whether the agreement is acceptable or not; acceptable limits must be defined a priori based on clinical, biological, or other relevant criteria. The Bland-Altman plot can also be used to express differences as percentages of the mean value, which is useful when the variability of differences increases with the magnitude of the measurement. This approach helps in assessing agreement relative to the true value. In addition to the Bland-Altman plot, other statistical methods such as correlation and regression are often used in method comparison studies. However, these methods are not suitable for assessing agreement between methods, as they focus on the relationship between variables rather than the differences between them. The Bland-Altman method provides a more accurate and comprehensive assessment of agreement between two measurement methods.