Page 56 - Glucose Monitoring Devices

54 CHAPTER 4 Consequences of SMBG systems inaccuracy

(metabolism). The patient may develop a fear of hypoglycemia [36e38] and over-
ride its therapy parameters (behavior) [39]. Frequent hypoglycemia may also lead to
decreased hypoglycemia awareness [40], increased glucose variability, and reduced
autonomic response during counterregulation [41]. This is in addition to intraday
and interday variability of the patient’s metabolism, exercise, stress, and other
hormonal changes. A different metabolic state will make the same BGM system
error have different effects.

Patient behavior is the main driver

Behavior is a fundamental part of this control system and, in the absence of auto-
mated insulin delivery systems, it is the main driver of glycemic control [42,43].
The stated (nominal) goal of this system is to properly control glucose; nevertheless,
patients have subtle, adaptive, and context-varying goals, such as reducing stress
[44], social pressure [45,46], and time required to manage their disease. Variability
in therapy modes, devices, drugs, and, most importantly, the natural physiological
variability often require patients to continuously adjust their behavior. Despite
efforts to standardize the management of diabetes, from the patient’s vintage point
diabetes management is still a heavy cognitive challenge requiring frequent adapta-
tion, which involves switching therapy modes, adjusting exercise, food intake,
hypoglycemia self-treatment, and insulin dosing strategies. This constantly chang-
ing environment makes it hard to isolate and adequately quantify what, if any, is
the contribution of BGM system accuracy to outcomes. In Fig. 4.3 we illustrate
some of these behaviors, following an approach similar to Ref. [47]. Upon entering

Hyperglycemia Hypoglycemia

Aware? Aware?

Ignore Ignore

Ignore Fingerstick Fingerstick Ignore

Denied Denied

OK Eating soon OK
(false) (false)
Treatment Carb
Ignore Bolus Exercise Eat Early
(medical eating)
Ignore Ignore
Eyeball
Follow
Functional Therapy
FIGURE 4.3
An example of choices around hypo/hyperglycemia.