# A quick note on CGM comparisons: MARD not that great a measure even though best we have

**URL:** <https://forum.fudiabetes.org/t/a-quick-note-on-cgm-comparisons-mard-not-that-great-a-measure-even-though-best-we-have/13634>\
**Category:** T2 Research\
**Tags:** cgm, dexcom, freestyle-libre\
**Created:** [March 2, 2023, 4:03am UTC](https://forum.fudiabetes.org/t/a-quick-note-on-cgm-comparisons-mard-not-that-great-a-measure-even-though-best-we-have/13634 "2023-03-02T04:03:52Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![GarLipow](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.fudiabetes.org/garlipow/32/10585_2.png) [@GarLipow](https://forum.fudiabetes.org/u/GarLipow)\
**Post date:** [March 2, 2023, 4:03am UTC](https://forum.fudiabetes.org/t/a-quick-note-on-cgm-comparisons-mard-not-that-great-a-measure-even-though-best-we-have/13634/1 "2023-03-02T04:03:52Z")

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In terms of formal comparisons between CGMs, MARD is the only numerical measure we have. But often people will note things along the line of “well that is great in the laboratory, but unfortunately I do not live in a lab.” Just wanted to note that formal research on MARD absolutely backs up your instinct on this. MARD is a very poor predictor of real world performance. It is an average, and does not allow for the difference and significance of different types of errors. In addition, different (valid) methods of conducting MARD studies will produce very different results. It can be gamed. Think of EPA MPG ratings on cars compared to actual mileage in real world driving. MARD is nowhere near that good a measure. Here is small sample of the articles out there on this.

Link: [Benefits and Limitations of MARD as a Performance Parameter for Continuous Glucose Monitoring in the Interstitial Space - PMC](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7189145/)

Link: [https://journals.sagepub.com/doi/pdf/10.1177/1932296816662047](https://journals.sagepub.com/doi/pdf/10.1177/1932296816662047)

[https://journals.sagepub.com/doi/10.1177/1932296815586013](https://journals.sagepub.com/doi/10.1177/1932296815586013)

> **[Limits to the Evaluation of the Accuracy of Continuous Glucose Monitoring...](https://www.mdpi.com/2079-6374/8/2/50)**
>
> Systems for continuous glucose monitoring (CGM) are evolving quickly, and the data obtained are expected to become the basis for clinical decisions for many patients with diabetes in the near future. However, this requires that their analytical...