title: Significance and Reliability of MARD for the Accuracy of CGM Systems.
abstract: There is a need to assess the accuracy of continuous glucose monitoring (CGM) systems for several uses. Mean absolute relative difference (MARD) is the measure of choice for this. Unfortunately, it is frequently overlooked that MARD values computed with data acquired during clinical studies do not reflect the accuracy of the CGM system only, but are strongly influenced by the design of the study. Thus, published MARD values must be understood not as precise values but as indications with some uncertainty.
  
  
  
  Data from a recent clinical trial, Monte Carlo simulations, and assumptions about the error distribution of the reference measurements have been used to determine the confidence region of MARD as a function of the number and the accuracy of the reference measurements.
  
  
  
  The uncertainty of the computed MARD values can be quantified by a newly introduced MARD reliability index (MRI), which independently mirrors the reliability of the evaluation. Thus MARD conveys information on the accuracy of the CGM system, while MRI conveys information on the uncertainty of the computed MARD values.
  
  
  
  MARD values from clinical studies should not be used blindly but the reliability of the evaluation should be considered as well. Furthermore, it should not be ignored that MARD does not take into account the key feature of CGM sensors, the frequency of the measurements. Additional metrics, such as precision absolute relative difference (PARD) should be used as well to obtain a better evaluation of the CGM performance for specific uses, for example, for artificial pancreas.
authors: 1 Institute for Design and Control of Mechatronical Systems, Johannes Kepler University, Linz, Austria.
authors: Florian
authors: F
authors: Reiterer
authors: 1 Institute for Design and Control of Mechatronical Systems, Johannes Kepler University, Linz, Austria.
authors: Philipp
authors: P
authors: Polterauer
authors: 2 Roche Diabetes Care Deutschland GmbH, Mannheim, Germany.
authors: Michael
authors: M
authors: Schoemaker
authors: 2 Roche Diabetes Care Deutschland GmbH, Mannheim, Germany.
authors: Guenther
authors: G
authors: Schmelzeisen-Redecker
authors: 3 Institute for Diabetes-Technology GmbH, at Ulm University, Ulm, Germany.
authors: Guido
authors: G
authors: Freckmann
authors: 4 Science & Co, Düsseldorf, Germany.
authors: Lutz
authors: L
authors: Heinemann
authors: 1 Institute for Design and Control of Mechatronical Systems, Johannes Kepler University, Linz, Austria.
authors: Luigi
authors: L
authors: Del Re
mesh_terms: D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000592:standards*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D006801:Humans; D012016:Reference Values
chemical_list: D001786:Blood Glucose
keywords: blood glucose; continuous glucose monitoring; diabetes therapy; glucose measurement; quality of measurement