Correspondence
Continuous Glucose Monitoring and Type 1 Diabetes
N Engl J Med 2009; 360:190-192January 8, 2009
- Article
To the Editor:
The Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group (Oct. 2 issue)1 concluded that “continuous glucose monitoring can be associated with improved glycemic control in adults with type 1 diabetes.” The authors assessed continuous glucose monitoring using three different devices (DexCom Seven, MiniMed Paradigm Real-Time Insulin Pump and Continuous Glucose Monitoring System, and FreeStyle Navigator). The evaluation of accuracy, performance, and reproducibility of different continuous-glucose-sensor systems is not straightforward, especially if taken in the context of established accuracy measures such as correlation or regression.2 It has been reported that the sensitivity of FreeStyle Navigator and MiniMed might vary and that further refinements in technology might be required before every system could be used for clinical purposes.3 Moreover, Kovatchev et al. found that the numerical errors of the DexCom device as compared with other tree devices were approximately 30% larger.4 The different analytic performances of the different continuous-glucose-sensor devices makes standardizing and harmonizing their measurements challenging. Thus, the potential problems stemming from the use of different continuous-glucose-monitoring systems should be acknowledged in evaluating results of multicenter clinical trials.
4 ReferencesMartina Montagnana, M.D.
Giuseppe Lippi, M.D.
Gian Cesare Guidi, M.D.
University of Verona, 37134 Verona, Italy
martina.montagnana@med. lu. se 1
The Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group
Full Text | Web of Science | Medline2
Parkes JL ,Slatin SL ,Pardo S ,Ginsberg BH . A new consensus error grid to evaluate the clinical significance of inaccuracies in the measurement of blood glucose. Diabetes Care 2000;23:1143-1148
CrossRef | Web of Science | Medline3
Clarke WL ,Anderson S ,Farhy L , et al. Evaluating the clinical accuracy of two continuous glucose sensors using continuous glucose-error grid analysis. Diabetes Care 2005;28:2412-2417
CrossRef | Web of Science | Medline4
Kovatchev B ,Anderson S ,Heinemann L ,Clarke W . Comparison of the numerical and clinical accuracy of four continuous glucose monitors. Diabetes Care 2008;31:1160-1164
CrossRef | Web of Science | Medline
To the Editor:
The Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group provides convincing evidence to support continuous glucose monitoring as a means of reducing glycated hemoglobin. The use of absolute and derivative functions from continuous glucose monitoring may also help limit the risk of hypoglycemia. The authors report rates of self-reported hypoglycemia that are similar to those in previous studies.1 However, their measure of mean time per day at a blood glucose level of 70 mg per deciliter (3.9 mmol per liter) or lower does not appear to have any clinical correlate. To exploit continuous monitoring in the management of hypoglycemia and capture episodes in patients with hypoglycemia unawareness, a consensus is required on what constitutes a hypoglycemic event in real time. The U.K. Hypoglycaemia Study Group defined a hypoglycemic event as 20 minutes or more with a blood glucose level of less than 54 mg per deciliter (3.0 mmol per liter).2 This compound measure reflects the duration and blood glucose level at which cognitive function deteriorates in physiological studies.3,4 Reanalysis of the data with a similar definition of biochemical hypoglycemia or further study of a more selected population is warranted to evaluate whether real-time monitoring offers any benefit in preventing hypoglycemia.
Alexander E.T. Finlayson, M.B., B.S., B.Med.Sci.
King's College Hospital, London SE5 9RS, United Kingdom
alexanderfinlayson@gmail.com Nathalie J. Cronin, M.B., B.S., B.Sc.
Jersey General Hospital, St Helier JE1 3QS, United KingdomPratik Choudhary, M.B., B.S.
King's College Hospital, London SE5 9RS, United KingdomDr. Choudhary reports receiving an honorarium from Medtronic. No other potential conflict of interest relevant to this letter was reported.
4 References1
Donnelly LA ,Morris AD ,Frier BM , et al. Frequency and predictors of hypoglycaemia in Type 1 and insulin-treated Type 2 diabetes: a population-based study. Diabet Med 2005;22:749-755
CrossRef | Web of Science | Medline2
UK Hypoglycaemia Study Group
CrossRef | Web of Science | Medline3
Deary IJ. Effects of hypoglycaemia on cognitive function. In: Frier BM, Fisher BM, eds. Hypoglycaemia and diabetes: clinical and physiological aspects. London: Edward Arnold, 1993:80-92.
4
Evans ML ,Pernet A ,Lomas J ,Jones J ,Amiel SA . Delay in onset of awareness of acute hypoglycemia and of restoration of cognitive performance during recovery. Diabetes Care 2000;23:893-897
CrossRef | Web of Science | Medline
Author/Editor Response
In response to Montagnana et al.: our trial was not a study to evaluate the accuracy of continuous glucose monitoring or to compare outcomes according to a specific device, but rather it was a clinical trial to evaluate the effectiveness of this technology when incorporated into daily diabetes management. Although future generations of continuous-glucose-monitoring devices are likely to have greater accuracy, we believe that the accuracy of the continuous-glucose-monitoring systems that are currently available commercially is sufficient for the devices to be beneficial. Our trial results support this. We found that most adults in the continuous-monitoring group used the device on a daily or near-daily basis for the duration of the trial and had a substantial decrease in the mean glycated hemoglobin level, as compared with the control group (P<0.001), without an increase in hypoglycemia. Children and adolescents in the continuous-monitoring group were less likely to use the continuous-glucose-monitoring device regularly, but those who did had a reduction in the glycated hemoglobin level that was of similar magnitude to the reduction seen in the adults (among subjects in the continuous-monitoring group, who averaged 6.0 or more days per week of continuous-glucose-monitor use over the 26-week period of the study, the mean decrease in the glycated hemoglobin level from baseline to 26 weeks was 0.5% in subjects ≥25 years old, 0.5% in those 15 to 24 years old, and 0.7% in those 8 to 14 years old).
In response to Finlayson et al.: the hypoglycemia event rate (≥20 minutes with a glucose level of <54 mg per deciliter), with combined data for the week after the 13-week visit and the week after the 26-week visit, was 0.25 event per 24 hours in the continuous-monitoring group and 0.33 event per 24 hours in the control group (P=0.03). Treatment-group differences in event rates ranged from 0.08 to 0.10 in the three age groups. These data provide further support for the ability of continuous glucose monitoring to reduce glycated hemoglobin levels in adults without increasing hypoglycemia.
William V. Tamborlane, M.D.
Yale University, New Haven, CT 06520Roy W. Beck, M.D., Ph.D.
Jaeb Center for Health Research, Tampa, FL 33647
rbeck@jaeb.org Lori Laffel, M.D., M.P.H.
Joslin Diabetes Center, Boston, MA 02215for the Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group
- Citing Articles (1)
Citing Articles
1
T. Danne, H. W. Valk, T. Kracht, K. Walte, R. Geldmacher, L. Sölter, W. Berge, Z. K. Welsh, J. R. Bugler, K. Lange, O. Kordonouri. (2009) Reducing glycaemic variability in type 1 diabetes self-management with a continuous glucose monitoring system based on wired enzyme technology. Diabetologia 52:8, 1496-1503
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