Evaluation of CGMS during rapid blood glucose changes in patients with type 1 diabetes

CGMS (Medtronic Minimed, Duesseldorf, Germany) allows continuous glucose monitoring. Recent studies with invasive monitoring techniques revealed discrepancies in blood glucose measurements obtained from different anatomical sites compared with those from the fingertip. The aim of this study was to investigate the CGMS and a device for alternative site testing (AST) during dynamic blood glucose changes and to compare these results with fingertip measurements.

Twelve patients with type 1 diabetes (seven women, five men; age, 33.3 +/- 8.7 years) received a 75-g oral glucose load. Insulin was applied intravenously (rapid glucose decline) or subcutaneously (moderate glucose decline) in a dosage between 3 to 18 units 2 h later in a randomized sequence on two different days. For continuous glucose measurements the CGMS standard sensor was inserted into the lower abdominal subcutis. Glucose measurements were obtained from the forearm using a minimally invasive technique (AST). CGMS and AST measurements were compared with glucose measurements obtained from the fingertip using a standard glucose oxidase method.

No significant difference could be observed among all three methods during increasing glucose levels. Insulin-induced blood glucose decline resulted in a significant time lag in the time course of blood glucose measurements obtained by AST compared with those obtained from the fingertip (P < 0.05, respectively). No significant difference could be observed between CGMS and fingertip measurements. Error grid analysis revealed 100% during rapid glucose fall and 98.5% during modest glucose fall of CGMS measurements within the clinically acceptable zones A and B.

Continuous glucose measurements using CGMS provide reliable glucose measurements even in the case of dynamic blood glucose changes.