Understanding Bland Altman analysis

Abstract

In a contemporary clinical laboratory it is very common to have to assess the agreement between two quantitative methods of measurement. The correct statistical approach to assess this degree of agreement is not obvious. Correlation and regression studies are frequently proposed. However, correlation studies the relationship between one variable and another, not the differences, and it is not recommended as a method for assessing the comparability between methods. In 1983 Altman and Bland (B&A) proposed an alternative analysis, based on the quantification of the agreement between two quantitative measurements by studying the mean difference and constructing limits of agreement. The B&A plot analysis is a simple way to evaluate a bias between the mean differences, and to estimate an agreement interval, within which 95% of the differences of the second method, compared to the first one, fall. Data can be analyzed both as unit differences plot and as percentage differences plot. The B&A plot method only defines the intervals of agreements, it does not say whether those limits are acceptable or not. Acceptable limits must be defined a priori, based on clinical necessity, biological considerations or other goals. The aim of this article is to provide guidance on the use and interpretation of Bland Altman analysis in method comparison studies.

Reproducibility of F18‐FDG PET radiomic features for different cervical tumor segmentation methods, gray‐level discretization, and reconstruction algorithms

“…We used the Bland–Altman analysis to evaluate the mean, standard deviation (SD), and upper/lower reproducibility limits (URL/LRL), Eqs. (4) and (5), for radiomic features in response to variation in each testing parameter 54, 55, 56$\text{URL}=\text{Mean}+(1.96\times SD)$ $\text{LRL}=\text{Mean}-(1.96\times SD)$ …”

“…We considered any feature below the low level as nonreproducible (NR). We based this approach on methods reported in several clinical studies 41, 53, 54, 55. Also, Galavis et al36 used a similar scale to categorize the features based on their variation, and Tixier et al37 indicated that such limits were referenced to previously defined reproducibility limits for standard uptake values.…”

Comparison of Methods of Mean Blood Pressure Calculation Using Ambulatory Blood Pressure Monitoring Results

“…It simply quantifies the bias and a range of agreement, within which 95 % of the differences between one measurement and the other are included [13]. However, there is no clinical evidence about clinical acceptable margin to evaluate the results.…”

Fast, accurate and easy-to-teach QT interval assessment: The triplicate concatenation method

“…A Bland-Altman plot was graphed [11,12]. The inferior and superior limits of agreement [LOA] were determined.…”