Spurious Reporting of Nocturnal Hypoglycemia by CGMS in Patients With Tightly Controlled Type 1 Diabetes

• Published in: Diabetes care Vol. 25; no. 9; pp. 1499 - 1503
• Main Authors: MCGOWAN, Kilty, THOMAS, William, MORAN, Antoinette
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.09.2002
• Subjects: Adolescent; Adult; Biological and medical sciences; Blood Glucose - analysis; Blood Glucose Self-Monitoring - standards; Circadian Rhythm; Diabetes; Diabetes Mellitus, Type 1 - diagnosis; Diabetes. Impaired glucose tolerance; Diagnostic Errors; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Female; Humans; Hypoglycemia; Hypoglycemia - diagnosis; Male; Management. Various non-drug treatments. Langerhans islet grafts; Medical sciences; Reproducibility of Results; Endocrinopathy; Human; Performance evaluation; Immunopathology; Controlled diabetes; Autoimmune disease; Hypoglycemia; Measuring instrument; Surveillance; Adolescent; Young adult; Insulin dependent diabetes; Automatic monitoring; Glycemia; Monitoring; Nocturnal variation; Computer aided analysis
• ISSN: 0149-5992; 1935-5548
• DOI: 10.2337/diacare.25.9.1499

Spurious Reporting of Nocturnal Hypoglycemia by CGMS in Patients With Tightly Controlled Type 1 Diabetes Kilty McGowan 1 , William Thomas , PHD 2 and Antoinette Moran , MD 3 1 Como Park High School, Minneapolis, Minnesota 2 Department of Biostatistics, University of Minnesota, Minneapolis, Minnesota 3 Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota Abstract OBJECTIVE —The Medtronic MiniMed Continuous Glucose Monitoring System (CGMS) is designed to continuously monitor interstitial fluid glucose levels within a range of 40–400 mg/dl. It is considered an important tool for overnight glucose monitoring. The goal of this study was to determine the accuracy of this system in individuals with tightly controlled diabetes. RESEARCH DESIGN AND METHODS —Seven adolescents and young adults with HbA 1c levels 6.6 ± 0.6% (range 5.7–7.1) were admitted to the Clinical Research Center. Simultaneous glucose measurements obtained by glucose analyzer, Accu-Check Advantage meter, and CGMS were compared. The analyzer levels were considered the standard. RESULTS —The CGMS results were lower than analyzer readings in 74% of simultaneous pairs of tests performed during the 24-h period; the average correlation was 0.76. There was a trend for the poorest correlation to occur in patients with the narrowest range in daily glucose levels. When the lowest CGMS reading of the night was compared with the simultaneous analyzer reading, the CGMS level was lower in all cases by an average of 38 ± 15%. In six of seven patients, the discrepancy was believed to be clinically significant; in at least four patients, overnight glucose levels reported by CGMS were falsely low, in a range that might have resulted in inappropriate reduction of overnight insulin dose. CONCLUSIONS —CGMS reports of asymptomatic nighttime hypoglycemia may be spurious and should be interpreted with caution in patients with tightly controlled diabetes. CGMS, Continuous Glucose Monitoring System Footnotes Address correspondence and reprint requests to Antoinette Moran, MD, University of Minnesota, Pediatric Department MMC 404, 516 Delaware St. SE, Minneapolis, MN 55455. E-mail: moran001{at}umn.edu . Received for publication 31 January 2002 and accepted in revised form 18 May 2002. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. DIABETES CARE