Error grid analysis

In 1993, we reported on a study of nine normal subjects using a wearable continuous monitoring system.17 This was the first application of error grid analysis... 

Figure 1.7 Clarke error grid analysis plot of the data of Figure 1.6.

Clarke WL, Anderson A, Farhy L, Breton M, Gonder-Frederick L, Cox D, Kovatchev B. Evaluating the clinical accuracy of two continuous glucose sensors using continuous glucose-error grid analysis. Diabetes Care 2005, 28, 2412-2417. 

Figure 3.2 The effect of prolonged subcutaneous implantation on biosensor function. Blood glucose values shown in solid circles and glucose sensor values in the continuous lines. The early study (top panel), but not the late study (bottom), shows excellent sensor accuracy and minimal lag between blood glucose and sensed glucose values. MARD (mean absolute relative difference) refers to a sensor accuracy metric. EGA refers to the Clarke error grid analysis accuracy metric.

The different manufacturers publish their own results in their user manuals. Mean absolute relative difference and bias results from the three manufacturers are shown in Table 5.2. The MARD measures indicates the average difference while the direction of the difference and the bias indicates if the differences are uniform or skewed to positive or negative values. The Clarke error grid analysis for the three manufacturers (Table 5.3) shows a wide difference in A zone results between the... 

Clarke error grid analysis of a study of 15 diabetic rats showed the percentage of readings that fell into the clinically correct regions (Zones A and B) increased from 92% to 96% when applying the Z-score rejection criteria.38 During the long-term implantation (25 4 days), Z-score calculations removed 32% of the individual sensor data from six fully implanted four-sensor arrays.39... 

Finally, the DT/MH AgFON was evaluated in vivo. A representative Clarke error grid analysis of a single rodent is shown in Figure 15.11. All measurements were taken from a single spot on the implanted DT/MH-functionalized AgFON surface. 

Error grid analysis has recently been extended for the evaluation of continuous glucose monitoring sensors. Kovatchev BP, Gonder-Frederick LA, Cox DJ, and Clarke WL. 2004. Evaluating the accuracy of continuous glucose-monitoring sensors. Diabetes Care 27 1922-1928. 

Kovalchev BP, Wakcman CA, Breton MD, Kost GJ, Louie RE, Tran NK, Klrmoff DC (2014) Computing the surveillance error grid analysis procedure and examples. J Diabetes Sci Technol 8(4) 673-684... 

We replace the integral from Si to S2 by a sum over a regular grid. We do this by applying first a variable transformation (to be specified by some criteria) such that after this transformation an equidistant grid can be used. An estimate of the discretization error is possible by means of tricky and non-trivial application of analysis. Details on this are given in the appendix, which is a rather important part of this paper. 

When Qp u(, . = 0(1) is accepted in some suitable grid norm (2 ) built into stability theorems, we might achieve economical factorized scheme (38) the error of approximation changes within a quantity of 0(r2). Following these procedures, we obtain economical factorized schemes of second-order accuracy in r as stated before due to the extra smoothness of the solution u. Such a stability analysis of schemes (36) and (39) is mostly based on the further treatment of the operators R and A as linear operators acting from... 

A more analytical method of stability analysis is the method of von Neumann [424, 565] (note that [424] is mostly incorrectly cited as being of the year 1951 [139]). The method focusses on an interior point along X in the grid and looks at the propagation of an error at that point, making certain reasonable assumptions, using Fourier series (which is why the method on occasion is also called the Fourier series method). 

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