Page 57 - Glucose Monitoring Devices

Quantifying the effect of inaccurate BGM systems 55

into hyperglycemia, a patient may be aware of it (physiology), make a decision
about confirming or not hyperglycemia (psychology), and upon confirmation, the
patient may opt to ignore or treat that condition (behavior). The patient’s treatment
may include bolusing or exercising. The impact of these behaviors is very significant
and, in some cases, drowns the effect of BGM system noise. More interestingly, in
some forms of therapy like continuous subcutaneous insulin infusion (CSII) or
sensor-augmented pump, behavioral “noise” may amplify the effect of BGM system
noise. For example [42], shows that missing boluses may not only be more impactful
than BGM system error but also make accuracy more critical as patients that skip
boluses have less opportunities to correct.

Effects spread over time and space
Self-treatment decisions based on inaccurate estimates of a patient’s plasma glucose
level may result in poor glycemic control. A BGM system that incorrectly reports a
high blood glucose level may drive a patient to hypoglycemia by administering an
unnecessary or unnecessarily large bolus (over bolus) [18,48,49]. In the most
extreme cases, measurement errors may result in severe hypoglycemia events
(SHE) requiring hospitalization [50]. Similarly, underestimated glucose levels
may drive the patient to hyperglycemia (under bolus). Chronic hyperglycemia in
the long term will manifest itself in higher hemoglobin A1c (HbA1c), increased
risk of diabetic ketoacidosis (DKA), and long-term clinical complications, such as
retinopathy, cardiac disease (congestive heart failure), and renal disease [51].
Ultimately, chronic clinical conditions will result in reduced quality of life,
increased cost of living, and increased cost of healthcare at a population level
[52e54]. As illustrated in Fig. 4.1, the consequences of an inaccurate meter span
the patient’s life and may eventually involve the entire organism. A limited, by no
means complete, classification of the effects comprises:
Clinical outcomes
The quality of glycemic control. We separate this into short term and long term.

Short term
Time in range, time in hypoglycemia, time in hyperglycemia; glucose variability;
risk of severe SHE and severe hyperglycemia (DKA).

Long term
HbA1c, diabetes-related complications: for example, retinopathy (up to blindness),
nephropathy (up to kidney failure, requiring transplantation or dialysis), diabetic
foot ulcer, amputation and vascular complications (including stroke, angina, heart
failure, myocardial infarction).

Quality of life
The effect of the disease in perceived quality of life. Examples are stress, anxiety,
and depression related to the disease. Quality of life lost due to the disease.