Confidence and coverage for Bland-Altman limits of agreement and their approximate confidence intervals

Carkeet, Andrew D. & Goh, Yee Teng (2016) Confidence and coverage for Bland-Altman limits of agreement and their approximate confidence intervals. Statistical Methods in Medical Research. (In Press)

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Bland and Altman described approximate methods in 1986 and 1999 for calculating confidence limits for their 95% limits of agreement, approximations which assume large subject numbers. In this paper, these approximations are compared with exact confidence intervals calculated using two-sided tolerance intervals for a normal distribution. The approximations are compared in terms of the tolerance factors themselves but also in terms of the exact confidence limits and the exact limits of agreement coverage corresponding to the approximate confidence interval methods. Using similar methods the 50th percentile of the tolerance interval are compared with the k values of 1.96 and 2, which Bland and Altman used to define limits of agreements (i.e. Formula+/− 1.96Sd and Formula+/− 2Sd). For limits of agreement outer confidence intervals, Bland and Altman’s approximations are too permissive for sample sizes <40 (1999 approximation) and <76 (1986 approximation). For inner confidence limits the approximations are poorer, being permissive for sample sizes of <490 (1986 approximation) and all practical sample sizes (1999 approximation). Exact confidence intervals for 95% limits of agreements, based on two-sided tolerance factors, can be calculated easily based on tables and should be used in preference to the approximate methods, especially for small sample sizes.

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ID Code: 99558
Item Type: Journal Article
Refereed: Yes
Keywords: Bland–Altman analysis, two-sided tolerance factors, limits of agreement, confidence limits, overage
DOI: 10.1177/0962280216665419
ISSN: 1477-0334
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Optometry & Vision Science
Copyright Owner: The Authors 2016
Deposited On: 27 Sep 2016 01:21
Last Modified: 27 Sep 2016 23:02

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