Agreement With Limits

Birgit Pauli-Haack  

b) About 95% of patients will have a difference in systolic blood pressure between the boundaries of concordance on Bland-Altman-Plot Bland J., Altman D. (1999): measurement agreement in method comparison studies. Statistical methods in medical research 8: 135-160. Myles – Cui. Use of the Bland-Altman method to measure compliance with repeated measurements. BJA: British Journal of Anaesthesia, Volume 99, issue 3, 1 September 2007, pages 309-311, doi.org/10.1093/bja/aem214. Excerpt from academic.oup.com/bja/article/99/3/309/355972 April 23, 2018 A Bland Altman (differential diagram) sheet in analytical chemistry or biomedicine is a method of presentation of data used in the analysis of the agreement between two different games. It is identical to a tube of average difference Tukey,[1] the name under which it is known in other areas, but it was popularized in the medical statistics of J. Martin Bland and Douglas G. Altman. [2] [3] Bland and Altman indicate that two methods developed to measure the same parameter (or property) should have a good correlation when a group of samples is selected in such a way as to vary the property to be determined considerably.

Therefore, a high correlation for two methods of measuring the same property could in itself be only a sign that a widely used sample has been chosen. A high correlation does not necessarily mean that there is a good agreement between the two methods. A significant correlation was established between systolic blood pressure as measured by the family physician and ambulatory systolic pressure per day (r-0.46). P<0.05). Physician measurements exceeded the measurements obtained through outpatient monitoring by an average of 18.9 mm Hg. The Bland-Altman method was used to present the difference in systolic blood pressure for each patient (GP minus outpatient daily monitoring) with the average of both measures (fig. 1⇓). Compliance limits are indicated by broken red lines, i.e. the two standard deviations of measurement differences on both sides of the average difference. Bland and Altman`s Lance [3] was number 29 in a list of the 100 most cited documents of all time, with more than 23,000 citations.

[8] Compliance limits estimate the interval between some of the differences between the measures. Now click on the arrow pointing down next to the “lower” row and change the type of Scatter diagram in a straight line, then click the OK button. I am often asked how I say the limits of concordance, if the two measurement methods correspond. What is a good deal and what would be bad? Bland-Altman plots are widely used to assess the agreement between two instruments or two measurement techniques. Bland-Altman plots identify systematic differences between measures (i.e. fixed pre-stress) or potential outliers. The average difference is the estimated distortion, and the SD of the differences measures random fluctuations around this average.