Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Mar;11(3):139-43.
doi: 10.1089/dia.2008.0044.

Graphical and numerical evaluation of continuous glucose sensing time lag

Boris P Kovatchev  1 , Devin Shields, Marc Breton
Affiliations

Graphical and numerical evaluation of continuous glucose sensing time lag

Boris P Kovatchev et al. Diabetes Technol Ther. 2009 Mar.

Abstract

Aim: This study introduces a new method for graphical and numerical evaluation of time lags typically associated with subcutaneous glucose sensing, based on Poincaré-type plot and a maximum statistical agreement criterion.

Methods: The proposed method is illustrated by retrospective analysis of 56 continuous glucose monitor (CGM) time series collected by the FreeStyle Navigator (Abbott Diabetes Care, Alameda, CA) from 28 patients with type 1 diabetes mellitus, each wearing simultaneously two sensors (on arm and abdomen) and parallel reference blood glucose (BG) collected with a reference YSI (Yellow Springs, OH) analyzer every 15 min. The average duration of a time series was 111 h; there were approximately 10,000 sensor-reference data pairs.

Results: When sliding in time CGM readings versus BG, the point of minimal spread of a Poincaré-type plot marks visually the time of CGM delay. The same point is numerically estimated by minimizing the distance between BG and CGM readings. The average observed time lag between reference BG and CGM was 12.5 min. Stratified by BG rate of change, the time lag was longer (16.8 min) when BG was falling, compared to steady or rising BG (11.7 min and 9.9 min, respectively) (P < 0.005). The time lags at the two sensor locations were not significantly different: 12.4 min on the arm, 12.6 min on the abdomen.

Conclusions: In this data set, substantial blood-to-sensor time delays were observed, possibly because of both blood-to-interstitial glucose transport and instrumental delay. Analysis of BG-CGM co-dynamics that is free from mathematical approximation of glucose fluctuations resulted in convenient visualization and numerical estimation of these delays.

PubMed Disclaimer

Figures

FIG. 1.
FIG. 1.
Poincaré plots of BG–sensor co-dynamics at delay values of (A) 30 min, (B) 22 min, (C) 15 min, (D) 7 min, and (E) 0 min. (F) AC achieves a maximum at 12.5 min, which coincides with the visual impression of minimal spread of the plot at 15 min.
FIG. 2.
FIG. 2.
Graphs of AC for sensors worn on the (A) arm and (B) abdomen, showing no difference between the sensor delays at the two sites.
See this image and copyright information in PMC

References

    1. Rebrin K. Steil GM. van Antwerp WP. Mastrototaro JJ. Subcutaneous glucose predicts plasma glucose independent of insulin: implications for continuous monitoring. Am J Physiol Endocrinol Metab. 1999;277:E561–E571. - PubMed
    1. Rebrin K. Steil GM. Can interstitial glucose assessment replace blood glucose measurements? Diabetes Technol Ther. 2000;2:461–472. - PubMed
    1. Steil GM. Rebrin K. Hariri F. Jinagonda S. Tadros S. Darwin C. Saad MF. Interstitial fluid glucose dynamics during insulin-induced hypoglycaemia. Diabetologia. 2005;48:1833–1840. - PubMed
    1. King CR. Anderson SM. Breton MD. Clarke WL. Kovatchev BP. Modeling of calibration effectiveness and blood-to-interstitial glucose dynamics as potential confounders of the accuracy of continuous glucose sensors during hyperinsulinemic clamp. J Diabetes Sci Technol. 2007;1:317–322. - PMC - PubMed
    1. Boyne M. Silver D. Kaplan J. Saudek C. Timing of changes in interstitial and venous blood glucose measured with a continuous subcutaneous glucose sensor. Diabetes. 2003;52:2790–2794. - PubMed

Publication types