A novel tool to relate glucose meter performance to clinical outcome: The Insulin Dose Error Assessment (IDEA) grid
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Background: The Clarke grid, Parkes error grids and Surveillance error grid were developed from expert opinion to assess the clinical accuracy of glucose meters. In the past decade there have been technological advances in the analytical performance of glucose meters and numerous insulin-dose protocols developed for local hospitalized and community patients. To relate accuracy of glucose tests and clinical use of insulin, an error grid could express glucose error in units of the ‘size of error of insulin dose’ administered, customized for the local insulin protocol for a specific patient group. Objective: To develop a grid to display the relationship between glucose error and the associated error in insulin dose, using an individual institutional insulin protocol. Methods: The effect of 0.5 mg/dL differences between reference and test methods on the risk of insulin dosing error was simulated using a published insulin dosing protocol (Karon et al., 2010). Data are displayed on a grid of reference glucose and meter glucose values with increasing color intensity applied as the size of clinical error in units of insulin dose errors increases. To evaluate a glucose meter, paired glucose data for the reference and test methods are plotted on the error grid and a histogram represents the frequency of insulin dose errors. Results: Figure 1. IDEA error grid analysis: Patient correlation data (n= 199) measured by reference and test glucose methods are plotted on the error grid. A frequency histogram of the insulin dose errors of the patient results depict 94.5% of insulin doses were within +/- 1 dose, 99.5% within +/- 2 doses. Conclusions: The IDEA grid is a useful tool that describes differences in glucose measurement in terms of insulin dosing error. This grid is capable of being individualized to an insulin dosing protocol to enable objective assessment of clinical risk attributed to analytic glucose meter error.