Page 26 - Glucose Monitoring Devices

The shortcomings of SMBG and future perspective 21

as 16%, suggesting uncommon use of data reporting and analysis to assist diabetes
self-management [110]. Easier to use seamless connectivity of blood glucose meter
with smartphone application and cloud-based storage of data may increase the use of
downloaded data in diabetes self-management [24].
Accuracy of SMBG is the basis of proper diabetes management. The require-
ments regarding the accuracy of blood glucose monitoring systems (BGMSs) are
defined in the ISO standards [26] and FDA guidance [27]. Although the approval
by regulatory agencies is based on their performance before market introduction,
postmarketing assessment of 18 commercially available BGMSs revealed that
only 6 of the 18 BGMSs fulfilled the latest ISO standard (ISO 15197-2013) [121].
In addition, user errors have been identified as a common cause of measurement
inaccuracy [122,123]. Nevertheless, BGMSs have to achieve the same accuracy
levels when used by trained personnel and intended users (laypersons). In the study
evaluating measurement accuracy of four different BGMSs in the hands of lay users
and trained personnel, BGMSs accuracy varied markedly depending on the operator.
Common lay user errors included not checking the test strip codes, incorrect appli-
cation of blood, and not using the blood drop immediately [124]. The authors
concluded that BGMSs insensitive to operator errors would be a useful improve-
ment. Inaccurate blood glucose levels can lead to incorrect treatment decisions
and adverse clinical outcomes [125]. In silico study showed a 10-fold increase in
missed hypoglycemic episodes when SMBG errors ranged from 10% to 20%
[126]. Similarly, a 30-day in silico study in T1D individuals on insulin pump therapy
showed that large error rate increased episodes of severe hypoglycemia, but had little
effect on HbA1c. On the other hand, glucose meter’s systematic bias affected HbA1c
as well as a number of severe hypoglycemia events. Both bias and error exhibited a
significant effect on total daily insulin and the number of necessary glucose
measurements per day [127].
SMBG a few times a day can reveal only rough patterns of daily blood glucose
variation. Consequently, high blood glucose excursions may be overlooked and low
blood glucose values may be undetected, especially in individuals with impaired
awareness of hypoglycemia [128]. CGM is a step further to optimal glycemic con-
trol [129]. In addition to current glucose, it provides information on direction and
velocity of glucose change [130]. CGM can improve metabolic control, reduces
the risk of hypoglycemia, increases time in normoglycemic range [131], and
improves quality of life [132]. A clear clinical benefit has been demonstrated in
outcome trials for people with T1D and T2D, using either MDI or CSII therapy
[133]. In addition, real-world use of CGM demonstrated reduction of costs related
to diabetes, which may outweigh CGM-related costs [134]. As CGM can now be
used for insulin treatment decision-making [135] and future devices might be
factory calibrated, it may be anticipated to replace SMBG in routine use for a
wide range of people with diabetes.