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SMBG underestimates glucose excursions in diabetes

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January 9, 2018

Although patients with diabetes accurately estimated their average blood glucose using self-monitoring, this method underestimated glucose excursions detected by continuous glucose monitoring, study data showed.

“It is common in clinical practice that [self-monitoring of blood glucose (SMBG)] records do not correlate with patients’ symptoms or HbA1c results,” Devna Mangrola, MD, of the department of internal medicine at the University of California at Davis, and colleagues wrote. “… This can happen even in those patients who follow the [SMBG] guidelines and instructions. In such cases, continuous glucose monitoring (CGM) can provide invaluable information.”

The researchers assigned 61 patients to CGM with the Medtronic iPRO2 system. The cohort included patients with both type 1 (n = 27) and type 2 (n = 34) diabetes. All patients continued self-monitoring while a clinical diabetes educator and/or registered nurse conducted continuous monitoring. Mangrola and colleagues reviewed data from 4 full days to assess differences in glucose values as reported by self-monitoring or continuous monitoring.

The lowest glucose value reported by patients conducting SMBG was approximately 25 mg/dL higher than that recorded by continuous monitoring, the researchers reported. This held true for patients with type 1 (P = .0232) and type 2 (P = .0003) diabetes. Further, Mangrola and colleagues wrote, the highest values reported with SMBG were 30 mg/dL lower than that detected by continuous monitoring among patients with type 1 diabetes (P = .0005), and 55 mg/dL lower in those with type 2 diabetes (P < .0001). There was no significant difference between the two methods in average blood glucose, however.

Glucose values were lowest during sleep and before breakfast, whereas the highest occurred postprandially and during the evening, the researchers reported.

“This study demonstrated that CGM uncovers glucose patterns that common [SMBG] patterns cannot; [SMBG] underestimates severity [of] hyperglycemia as well as hypoglycemia,” Mangrola and colleagues wrote. “… Our findings make a strong case for [SMBG] after meals, especially in the evenings and in [type 2 diabetes] patients. Additional research is necessary to determine whether postprandial [SMBG] can improve overall glycemic control.” – by Andy Polhamus

Disclosures: The authors report no relevant financial disclosures.