Page 11 - Glucose Monitoring Devices

6 CHAPTER 1 Introduction to SMBG

portable, easier to use, and cheaper devices made SMBG more applicable, and their
use steadily increased [6]. In view of this widespread use of SMBG, the American
Diabetes Association (ADA) convened the first consensus statement on SMBG in
1987 [42]. The landmark Diabetes Control and Complications Trial (DCCT) was
the first long-term randomized prospective study to ascertain whether intensive ther-
apy aimed at near-normal glycemic control could reduce microvascular complica-
tions as compared to standard diabetes care among people with T1D. Near-
normal glycemic control included preprandial blood glucose concentrations
between 70 and 120 mg/dL, postprandial concentrations of less than 180 mg/dL, a
weekly 3 a.m. measurement greater than 65 mg/dL, and hemoglobin A1c
(HbA1c), measured monthly, within the normal range (less than 6.05%). Intensive
glycemic control was guided by frequent SMBG ( 4 times daily) as a tool for insu-
lin dose titration to achieve normal blood glucose levels, whether in standard therapy
once-daily SMBG generally did not guide insulin supplementation. In 1993, the
DCCT confirmed that intensive diabetes management dramatically reduced the
risk of microvascular complications in T1D. Thus the study resolved the controversy
about the effect of glycemic control on microvascular complications of diabetes
[43]. Following the DCCT, intensive therapy became the standard of care in the
management of T1D and the value of SMBG as an integral part of intensive therapy
was generally accepted [44]. Eleven years after the conclusion of the DCCT, the
follow-up observational Epidemiology of Diabetes and its Complications (EDIC)
study of the DCCT cohort demonstrated the long-lasting favorable effect of intensive
therapy on the risk of macrovascular complications despite the minor differences in
mean HbA1c between the groups over the follow-up period [45]. The long-lasting
beneficial effects of intensive therapy on the incidence of cardiovascular diseased
termed “metabolic memory”dcontinues after over 30 years of follow-up [46].
Due to the higher glucose variability in persons with T1D, greater SMBG fre-
quency generally correlated with lower HbA1c. In addition, reanalyzed DCCT
data demonstrated that within-day blood glucose standard deviationas a measure
of glycemic variability predicted hypoglycemia independently of HbA1c [47].
Following the DCCT, several studies have confirmed a strong association between
increased frequency of SMBG and lower HbA1c levels [48e50]. Moreover, one
additional SMBG per day resulted in an HbA1c reduction of 0.26% corrected for
age, gender, diabetes duration, insulin therapy, and center difference [51]. Data anal-
ysis of more than 20,000 children and adults from the T1D Exchange Registry
showed a strong association between a higher number of SMBG measurements
per day and lower HbA1c across a wide age range. The association was present in
both continuous subcutaneous insulin infusion (CSII) and multiple daily injections
(MDI) users. The difference between measuring 3e4 times per day and
measuring 10 times per day has been shown to affect HbA1c of about 1%. The
association between SMBG and HbA1c appeared to level-off at approximately 10
SMBG measurements per day [52]. Similarly, adults with T1D under excellent con-
trol (HbA1c < 6.5%) performed SMBG more frequently, including more frequent
SMBG measurements before giving a bolus compared to individuals under poor
control (HbA1c 8.5%) [53].