Detection of Hypoglycemia With the GlucoWatch Biographer

Pitzer, Kenneth R. DVM
Desai, Shashi BS
Dunn, Tim BS
Edelman, Steve MD
Jayalakshmi, Yalia PHD
Kennedy, John BS
Tamada, Janet A. PHD
Potts, Russell O. PHD

From ¹Cygnus Incorporated, Redwood City; and the ²UCSD School of Medicine and Veterans Affairs Medical Center, San Diego VA Medical Center, San Diego, California.

Address correspondence and reprint requests to Dr. Pitzer, Cygnus, Inc., 400 Penobscot Dr., Redwood City, CA 94063. E-mail: [email protected].

Received for publication 16 August 2000 and accepted in revised form 8 January 2001.

S.E., J.K., and T.D. are paid consultants for and hold stock in Cygnus; and K.R.P., Y.J., J.A.T., R.O.P., and S.D. are employed by and hold stock in Cygnus.

Abbreviations: AUC, area under the curve; FN, false negative; FP, false positive; FPF, FP fraction; PTH, parathyroid hormone; ROC, receiver operator characteristic; TN, true negative; TP, true positive; TPF, TP fraction.

A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

Diabetes Care 24(5):p 881-885, May 2001.

OBJECTIVE

Hypoglycemia is a common acute complication of diabetes therapy. The GlucoWatch biographer provides frequent and automatic glucose measurements with an adjustable low-glucose alarm. We have analyzed the performance of the biographer low-glucose alarm relative to hypoglycemia as defined by blood glucose ≤3.9 mmol/l.

RESEARCH DESIGN AND METHODS

The analysis was based on 1,091 biographer uses from four clinical trials, which generated 14,487 paired (biographer and blood glucose) readings.

RESULTS

The results show that as the low-glucose alert level of the biographer is increased, the number of true positive alerts (alarm sounds and blood glucose ≤3.9 mmol/l) and false positive alerts (alarm sounds but blood glucose >3.9 mmol/l) increased. When analyzed as a function of varying low-glucose alert levels, the results show receiver operator characteristic curves consistent with a highly useful diagnostic tool. Setting the alert level from 1.1 to 1.7 mmol/l above the level of concern is likely to optimize the trade-off between true positives and false positives for each user. When the same blood glucose data are analyzed for typical monitoring practices (two or four measurements per day), the results show that fewer hypoglycemic events are detected than those detected with the biographer.

CONCLUSIONS

The frequent and automatic nature of the biographer readings allows more effective detection of hypoglycemia than that achieved with current medical practice.