A Simple and Robust Alternative to Bland-Altman Method of Assessing Clinical Agreement

Abstract

Clinical agreement between two quantitative measurements on a group of subjects is generally assessed with the help of the Bland-Altman (B-A) limits. These limits only describe the dispersion of disagreements in 95% cases and do not measure the degree of agreement. The interpretation regarding the presence or absence of agreement by this method is based on whether B-A limits are within the pre-specified externally determined clinical tolerance limits. Thus, clinical tolerance limits are necessary for this method. We argue in this communication that the direct use of clinical tolerance limits for assessing agreement without the B-A limits has tremendous merits. This nonparametric approach is simple, is robust to the distribution pattern and outliers, has more flexibility, and is more effective in assessing the degree of clinical agreement. This is illustrated with the help of two examples, including setups where clinical tolerance limits can be set up to follow varying trends if required in the clinical context – a feature not available in the B-A method.

Note:
Funding Information: None.

Conflict of Interests: None.

Keywords: Agreement analysis, Bland-Altman method, Clinical tolerance limits, Limits of agreement, Nonparametric approach, Robust method