Limitations of Conventional Methods of Self-Monitoring of Blood Glucose

Abstract

OBJECTIVE—Children with type 1 diabetes are usually asked to perform self-monitoring of blood glucose (SMBG) before meals and at bedtime, and it is assumed that if results are in target range, along with HbA1c measurements, then overall glycemic control is adequate. However, the brief glimpses in the 24-h glucose profile provided by SMBG may miss marked glycemic excursions. The MiniMed Continuous Glucose Monitoring System (CGMS) has provided a new method to obtain continuous glucose profiles and opportunities to examine limitations of conventional monitoring. RESEARCH DESIGN AND METHODS—A total of 56 children with type 1 diabetes (age 2–18 years) wore the CGMS for 3 days. Patients entered four fingerstick blood samples into the monitor for calibration and kept records of food intake, exercise, and hypoglycemic symptoms. Data were downloaded, and glycemic patterns were identified. RESULTS—Despite satisfactory HbA1c levels (7.7 ± 1.4%) and premeal glucose levels near the target range, the CGMS revealed profound postprandial hyperglycemia. Almost 90% of the peak postprandial glucose levels after every meal were >180 mg/dl (above target), and almost 50% were >300 mg/dl. Additionally, the CGMS revealed frequent and prolonged asymptomatic hypoglycemia (glucose <60 mg/dl) in almost 70% of the children. CONCLUSIONS—Despite excellent HbA1c levels and target preprandial glucose levels, children often experience nocturnal hypoglycemia and postprandial hyperglycemia that are not evident with routine monitoring. Repeated use of the CGMS may provide a means to optimize basal and bolus insulin replacement in patients with type 1 diabetes.