System Accuracy Assessment of a Blood Glucose Meter With Wireless Internet Access Associated With Unusual Hypoglycemia Patterns in Clinical Trials

Impact of Blood Glucose Monitoring System Accuracy on Clinical Decision Making for Diabetes Management

BACKGROUND

The accuracy of blood glucose monitoring systems (BGMS) is crucial for the safe and effective management of diabetes mellitus. Despite standardization of accuracy assessment procedures and requirements, various studies have shown that the accuracy of BGMS on the market can vary considerably. This article therefore provides health care professionals and users with an intuitive illustration of the impact of BGMS accuracy on clinical decision making.

MATERIAL AND METHODS

Several hypothetical patient scenarios based on blood glucose (BG) levels in the low, normal, and high BG range are devised. Using data from a recent BGMS accuracy study, a method for calculating the expected range of BG readings from four examined BGMS at the selected BG levels is introduced. Based on these ranges, it is illustrated how clinical decisions and subsequent outcomes of the hypothetical patients are affected by the expected inaccuracies of the BGMS.

RESULTS

The range of expected BGMS readings for the same true BG level can vary considerably between different BGMS. The discussion of hypothetical patient scenarios revealed that the use of some BGMS could be associated with an increased risk of adverse events such as failure to detect hypoglycemia, driving with an unsafe BG level, delay of treatment intervention in diabetes during pregnancy, or the failure to prevent diabetic ketoacidosis.

CONCLUSIONS

This article can support both health care professionals and patients to understand the impact of BGMS accuracy in a relatable, clinical context. Furthermore, it is suggested that current accuracy requirements might be insufficient for the prevention of adverse clinical outcomes in certain circumstances.

How conclusive is the CONCLUDE trial?

The development of basal insulin analogues has reduced the risk of hypoglycaemia in insulin-treated individuals with type 2 diabetes. Insulin degludec and insulin glargine 300 U/ml (glargine U300) represent an evolution of basal insulin analogues, both of them reducing the risk of hypoglycaemia as compared with that associated with glargine U100. However, whether degludec and glargine U300 are equivalent with respect to glycaemic control and risk of hypoglycaemia remains to be fully ascertained. In the CONCLUDE trial, 1609 individuals with type 2 diabetes were randomised to either degludec 200 U/ml (degludec U200) or glargine U300. In this issue of Diabetologia (https://doi.org/10.1007/s00125-019-05080-9) the investigators report that during the maintenance period, HbA_1c improved to a similar extent in the two groups with no significant difference in the rate of overall hypoglycaemia (the primary endpoint of the study), while rates of nocturnal symptomatic and severe hypoglycaemia (secondary endpoints) were lower with degludec U200 than with glargine U300. These results, although of great interest to the clinician, need to be carefully interpreted as they cannot be considered as conclusive. First, the primary endpoint was not met and, therefore, analyses of secondary endpoints remain exploratory. Even assuming that degludec is superior to glargine in reducing the risk of hypoglycaemia, the mechanism(s) accounting for such an advantage remain elusive and potential differences in pharmacokinetics and pharmacodynamics difficult to appreciate because of methodological issues. The study design had to be amended because of lack of reliability of the glucometers initially used in the trial, particularly in the low blood glucose ranges, so the potential implications of these changes in the subsequent conduct of the trial cannot be excluded. Finally, comparison with the BRIGHT trial, the only other available head-to-head study, is complicated by differences between the two studies in the primary endpoint (HbA_1c reduction vs reduction of the risk of hypoglycaemia), study population (insulin-experienced vs insulin-naive) and concomitant glucose-lowering medications. In spite of all this, CONCLUDE teaches us an important lesson regarding the need, particularly in the clinical setting, to monitor the reliability of the glucometers the diabetic individual uses to adjust his/her insulin dose. Insufficient precision or inappropriate use of the glucometer can easily offset any minute advantage a new insulin can offer with respect to glycaemic control and risk of hypoglycaemia.

System accuracy assessments with a blood glucose meter with combined glucose and ß-hydroxybutyrate measurement capabilities

Background: We evaluated the Wellion Galileo GLU/KET blood and ketone (ß-Hydroxybutyrate, ß-OHB) meter to demonstrate that it meets ISO15107:2015 regulatory approval criteria. Research Design and Methods: A total of 100 subjects (52 female, age: 30 to 84 years, diabetes: 10 type 1/90 type 2) with blood glucose levels distributed over the entire measurement range as required by the ISO15197 protocol were tested (double determinations with 3 strip lots and two devices). A similar test protocol was followed to test ß-OHB strip performance (reference devices: YSI 2300plus for glucose and STANBIO ß-HOB LiquiColor TestKit for ß-OHB). Precision was tested for glucose with 3 blood glucose concentrations (ß-OHB: 2 control solutions). Results: All glucose test-strip lots met the strict ISO acceptance criteria. Mean absolute relative difference (MARD) was 4.9% and all data pairs were in zone A of the consensus error grid. The ß-OHB test-strips also met the pre-defined acceptance criteria. Within-run and between-run precision was calculated to be 2.3% and 0.7% for the glucose strips (3.7%/0.8% for the ketone strips). Conclusions: When tested according to the ISO15197:2015 guideline, the device showed very accurate measurement performance for glucose and ß-OHB testing and fully met regulatory accuracy approval criteria.

Laboratory Evaluation of Linearity, Repeatability, and Hematocrit Interference With an Internet-Enabled Blood Glucose Meter

BACKGROUND

In recent clinical trials, use of the MyGlucoHealth blood glucose meter (BGM) and electronic diary was associated with an unusual reporting pattern of glycemic data and hypoglycemic events. Therefore, the performance of representative BGMs used by the patients was investigated to assess repeatability, linearity, and hematocrit interference in accordance with regulatory guidelines.

METHOD

Ten devices and 6 strip lots were selected using standard randomization and repeatability procedures. Venous heparinized blood was drawn from healthy subjects, immediately aliquoted and adjusted to 5 target blood glucose (BG) ranges for the repeatability and 11 BG concentrations for the linearity tests. For the hematocrit interference test, each sample within 5 target BG ranges was split into 5 aliquots and adjusted to hematocrit levels across the acceptance range. YSI 2300 STAT Plus was used as the laboratory reference method in all experiments.

RESULTS

Measurement repeatability or precision was acceptable across the target BG ranges for all devices and strip lots with coefficient of variation (CV) between 3.4-9.7% (mean: 5.7%). Linearity was shown by a correlation coefficient of .991; however, a positive bias was seen for BG <100 mg/dL (86% measurements did not meet ISO15197:2015 acceptance criteria). Significant hematocrit interference (up to 20%) was observed for BG >100 mg/dL (ISO15197:2015 acceptance criteria: ±10%), while the results were acceptable for BG <100 mg/dL.

CONCLUSIONS

The BGM met repeatability requirements but demonstrated a significant measurement bias in the low BG range. In addition, it failed the ISO15197:2015 criteria for hematocrit interference.

Efficacy and Safety of Degludec Compared to Glargine 300 Units/mL in Insulin-Experienced Patients With Type 2 Diabetes: Trial Protocol Amendment (NCT03078478)

BACKGROUND

A head-to-head trial (NCT03078478) between insulin degludec and insulin glargine U300 with the primary objective of comparing the risk of hypoglycemia is being conducted. During trial conduct, safety concerns related to the glycemic data collection system led to a postinitiation protocol amendment, described here.

METHODS

This randomized (1:1), open-label, treat-to-target, multinational trial was initiated in March 2017 with a planned treatment period of 52 weeks (16 weeks titration + 36 weeks maintenance). Overall, ~1600 insulin-experienced patients at risk of developing hypoglycemia based on predefined risk factors were included. The protocol amendment implemented in February 2018 resulted in assuring patient safety and an extension of the total treatment period up to 88 weeks (16 weeks titration + variable maintenance 1 + 36 weeks maintenance 2). The original glycemic data collection system (MyGlucoHealth blood glucose meter + electronic diary) was discontinued because of safety concerns and replaced with an Abbott blood glucose meter and paper diary to collect self-measured blood glucose and hypoglycemic episodes. The primary endpoint of number of severe or blood-glucose confirmed symptomatic hypoglycemic episodes will be evaluated with the same analysis duration and statistical methods as the original protocol. Only relevant changes were implemented to maintain patient safety while permitting evaluation of the scientific objectives of the trial.

CONCLUSIONS

These observations highlight the importance of safety surveillance during trial conduct despite the use of currently marketed glucose monitoring devices. The prompt protocol amendment and ensuing actions ensured that the scientific integrity of the trial was not compromised.