title: GlucoWatch G2 Biographer alarm reliability during hypoglycemia in children.
abstract: BACKGROUND
  The GlucoWatch G2 Biographer (GW2B) (Cygnus, Inc., Redwood City, CA) provides near-continuous monitoring of glucose values in near real time. This device is equipped with two types of alarms to detect hypoglycemia. The hypoglycemia alarm is triggered when the current glucose measurement falls below the level set by the user. The "down alert" alarm is triggered when extrapolation of the current glucose trend anticipates hypoglycemia to occur within the next 20 min.
  
  
  METHODS
  We used data from an inpatient accuracy study to assess the performance of these alarms. During a 24-h clinical research center stay, 89 children and adolescents with Type 1 diabetes mellitus (3.5-17.7 years old) wore 174 GW2B devices and had frequent serum glucose determinations during the day and night.
  
  
  RESULTS
  Sensitivity to detect hypoglycemia (reference glucose < or = 60 mg/dL) during an insulin-induced hypoglycemia test was 24% with the hypoglycemia alarm alone and 88% when combined with the down alert alarm. Overnight sensitivity from 11 p.m. to 6 a.m. was 23% with the hypoglycemia alarm alone and 77% when combined with the down alert alarm. For 16% of hypoglycemia alarms, the reference glucose was above 70 mg/dL for 30 min before and after the time of the alarm. For the two alarm types combined, the corresponding false-positive rate increased to 62%.
  
  
  CONCLUSIONS
  The down alert alarm substantially improves the sensitivity of the GW2B to detect hypoglycemia at the price of a large increase in the false alarm rate. The utility of these alarms in the day-to-day management of children with diabetes remains to be determined.
authors.affiliation: DirecNet Coordinating Center, Jaeb Center for Health Research, Tampa, FL 33647, USA. direcnet@jaeb.org
authors.forename: Eva
authors.initials: E
authors.lastname: Tsalikian
authors.forename: Craig
authors.initials: C
authors.lastname: Kollman
authors.forename: Nelly
authors.initials: N
authors.lastname: Mauras
authors.forename: Stuart
authors.initials: S
authors.lastname: Weinzimer
authors.forename: Bruce
authors.initials: B
authors.lastname: Buckingham
authors.forename: Dongyuan
authors.initials: D
authors.lastname: Xing
authors.forename: Roy
authors.initials: R
authors.lastname: Beck
authors.forename: Katrina
authors.initials: K
authors.lastname: Ruedy
authors.forename: William
authors.initials: W
authors.lastname: Tamborlane
authors.forename: Rosanna
authors.initials: R
authors.lastname: Fiallo-Scharer
mesh_terms: D000293:Adolescent; D000465:Algorithms; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000188:drug therapy; D004868:Equipment Failure; D006801:Humans; D007003:Hypoglycemia / Q000097:blood / Q000175:diagnosis* / Q000517:prevention & control; D007297:Inpatients; D007328:Insulin / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use; D018670:Monitoring, Ambulatory / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D001786:Blood Glucose; D007328:Insulin