The Chemistry of Commercial Continuous Glucose Monitors

The analytical methodologies of the continuous glucose monitors (CGMs) commercialized to date are described. The devices include two noninvasive products: the GlucoWatch(R) (Cygnus, Redwood City, CA) G2 Biographer uses iontophoresis to obtain a sample and electrochemistry for glucose detection, and PENDRA(R) (Pendragon Medical Ltd., Zurich, Switzerland) utilizes impedance spectroscopy. Three minimally invasive systems employ subcutaneous amperometric sensors-Guardian REAL-Time (Medtronic MiniMed, Sylmar, CA), DexCom(TM) STS(TM)-7 (DexCom, San Diego, CA), and FreeStyle Navigator(TM) (Abbott Diabetes Care, Alameda, CA). The GlucoDay(R) (A. Menarini I. F. R. S. r. l., Florence, Italy) collects a sample with a minimally invasive microdialysis fiber and measures the glucose electrochemically.