Discrepancies in glycemic metrics derived from different continuous glucose monitoring systems in adult patients with type 1 diabetes mellitus

The Need for Standardization of Continuous Glucose Monitoring Performance Evaluation: An Opinion by the International Federation of Clinical Chemistry and Laboratory Medicine Working Group on Continuous Glucose Monitoring

Metrics derived from continuous glucose monitoring (CGM) systems are often discordant between systems. A major cause is that CGM systems are not standardized; they use various algorithms and calibration methods, leading to discordant CGM readings across systems. This discordance can be addressed by standardizing CGM performance assessments: If manufacturers aim their CGM systems at the same target, then CGM readings will align across systems. This standardization should include the comparator device, sample origin, and study procedures. With better aligned CGM readings, CGM-derived metrics will subsequently also align better between systems.

Comparing the glycaemic outcomes between real-time continuous glucose monitoring (rt-CGM) and intermittently scanned continuous glucose monitoring (isCGM) among adults and children with type 1 diabetes: A systematic review and meta-analysis of randomized controlled trials

AIM

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing the effectiveness of real-time continuous glucose monitoring (rtCGM) versus intermittently scanned continuous glucose monitoring (isCGM) on key glycaemic metrics (co-primary outcomes HbA1c and time-in-range [TIR] 70-180 mg/dL, 3.9-10.0 mmol/L) among people with type 1 diabetes (T1D).

METHODS

Medline, PubMed, Scopus, Web of Science and Cochrane Central Register of clinical trials were searched. Inclusion criteria were RCTs; T1D populations of any age and insulin regimen; comparing any type of rtCGM with isCGM (only the first generation had been compared to date); and reporting the glycaemic outcomes. Glycaemic outcomes were extracted post-intervention and expressed as mean differences and 95% CIs between the two comparators. Results were pooled using a random-effect meta-analysis. The risk of bias was assessed using the Cochrane RoB2 tool. The quality of evidence was assessed by the GRADE approach.

RESULTS

Five RCTs met the inclusion criteria (4 parallel and 1 crossover design; 4 with CGM use <8 weeks), involving 446 participants (354 adults; 92 children and adolescents). Overall, meta-analysis showed rtCGM compared to isCGM improved absolute TIR by +7.0% (95% CI: 5.8%-8.3%, I2  = 0%, p < 0.01) accompanied by a favorable effect on time-below-range <70 mg/dL (3.9 mmol/L) - 1.7% (95%CI: -3.0% to -0.4%; p = 0.03). No differences were seen regarding HbA1c.

CONCLUSIONS

This meta-analysis highlights that for people with T1D, rtCGM confers benefits over isCGM primarily related to increased TIR, with improvements in hypo- and hyperglycaemia.

Mixed Meal Tolerance Test Versus Continuous Glucose Monitoring for an Effective Diagnosis of Persistent Post-Bariatric Hypoglycemia

Gastric bypass determines an increase in incretin secretion and glucose excursions throughout the day and may sometimes entail the development of severe post-bariatric hypoglycemia (PBH). However, there is no consensus on the gold standard method for its diagnosis. In this study, we evaluated the usefulness of a mixed meal tolerance test (MMTT) and continuous glucose monitoring (CGM) for the diagnosis of PBH, defined as glucose levels <54 mg/dL (3.0 mmol/L). We found that hypoglycemia occurred in 60% of patients after the MMTT and in 75% during CGM, and it was predominantly asymptomatic. The MMTT confirmed the diagnosis of PBH in 88.9%of patients in whom surgery had been performed more than three years ago, in comparison to 36.4% in cases with a shorter postsurgical duration. CGM diagnosed nocturnal asymptomatic hypoglycemia in 70% of patients, and daytime postprandial hypoglycemia in 25% of cases. The mean duration of asymptomatic hypoglycemia was more than 30 min a day. Patients with ≥2% of their CGM readings with hypoglycemia exhibited a higher degree of glucose variability than those with <1% of the time in hypoglycemia. Our results show that the MMTT may be a useful dynamic test to confirm the occurrence of hypoglycemia in a large number of patients with persistent and recurrent PBH during long-term follow-up after gastric bypass. CGM, on its part, helps identify hypoglycemia in the real-world setting, especially nocturnal asymptomatic hypoglycemia, bringing to light that PBH is not always postprandial.