The Need for Separate Performance Goals for Glucose Sensors in the Hypoglycemic, Normoglycemic, and Hyperglycemic Ranges
- David C. Klonoff, MD, FACP
- From Diabetes Technology & Therapeutics, Mills-Peninsula Health Services Diabetes Research Institute, 100 South San Mateo Dr., Room 3124, San Mateo, California
- Address correspondence to David C. Klonoff, MD, FACP, Diabetes Technology & Therapeutics, Mills-Peninsula Health Services Diabetes Research Institute, 100 South San Mateo Dr., Room 3124, San Mateo, CA 94401. E-mail: klonoff{at}itsa.ucsf.edu
Blood glucose monitors are an important tool for people with diabetes to assess their physiological status and allow them to properly dose themselves with medication or food. The need to adjust the amount of treatment is greatest when the blood glucose level is in the hypoglycemic range because of the risk of acute brain damage if the condition is not quickly treated. A variety of technologies are available to assist patients with detecting hypoglycemia. How accurate are the various types of technologies at detecting hypoglycemia? Are the new continuous glucose monitoring technologies as accurate as current performance guidelines for home blood glucose monitors specify?
In this issue of Diabetes Care, the Diabetes Research in Children Network (DirecNet) collaborative study group concludes (1) that the GlucoWatch G2 Biographer (GW2B) and continuous glucose monitoring systems (CGMSs) do not reliably detect hypoglycemia in children and adolescents. They noted that as few as 31% of GW2B values and as few as 42% of CGMSs (including both first- and second-generation sensors) were within 15 mg/dl of reference serum values. When a hypoglycemia alarm value was set at 60 mg/dl, the GW2B demonstrated that the sensitivity to detect hypoglycemia was 23%, the specificity to detect hypoglycemia was 49%, and the false-alarm incidence was 51%.
The two continuous glucose monitors probably performed less accurately in this DirecNet study than many clinicians would expect of new technology that has been approved by the U.S. Food and Drug Administration within the past few years. The performance statistics for glucose monitoring systems that are frequently quoted from the literature or from the package inserts of manufacturers mostly derive from studies that measure patients whose blood glucose levels can be low, normal, or high. Because most patients spend little time in a state of hypoglycemia, the majority of data points …
