Endocrine Abstracts

Introduction: Haemoglobin A1c (HbA1c) is the gold standard for evaluating glycaemic control in people with diabetes (1). In recent years continuous glucose monitoring (CGM) has introduced new parameters, including glucose management index (GMI), a calculation based on mean glucose that provides an estimation of HbA1c (2-4). However, in some patients GMI and HbA1c differ significantly (2, 5-9). The aim of this study is to investigate whether a difference between HbA1c and GMI, expressed as haemoglobin glycation index (HGI), has an impact on the prevalence of microvascular complications in people with type 1 diabetes mellitus.

Methods: This retrospective, cross-sectional study included adults with type 1 diabetes using CGM. Exclusion criteria included pregnancy, dialysis or insufficient sensor use (<70% over 28 days). The presence of microvascular complications was compared across HGI subgroups (low ≤-0.5%, moderate -0.5% to 0.5%, high ≥0.5%). Logistic regression analyses evaluated the independent association between HGI and microvascular complications.

Results: Three hundred sixty-nine adults (57.7% men, median diabetes duration 27.7 years) were included. The median HbA1c was 7.1% (6.5-7.6), GMI was 7.1% (6.7-7.5), and HGI was -0.10% (-0.47 to 0.26). In 144 participants (39%), the absolute difference between HbA1c and the GMI was ≥0.5%, and in 31 individuals (8.4%) the difference was even ≥1% (Figure 1). Eighty-five participants (23%) had a low HGI and 59 (16%) had a high HGI. Compared to low HGI high HGI was associated with significantly higher rates of nephropathy (4% vs 19%, P = 0.016), neuropathy (6% vs 20%, P = 0.011) and severe retinopathy (15% vs 33%, P = 0.026, figure 2). Logistic regression showed that high HGI was associated with nephropathy (OR 2.23), neuropathy (OR 3.15), and severe retinopathy (OR 2.26). However, after adjusting for co-variates (diabetes duration, smoking, hypertension) the associations lost significance.

Conclusion: This study demonstrates that a high HGI based on CGM data may serve as a valuable parameter in daily clinical practice for identifying individuals at higher risk of microvascular complications. These results strengthen the rationale for prospective studies to confirm the clinical relevance of HGI and to further define its role in complication risk stratification.

Figure 1: Discrepancy between HbA1c and GMI

Figure 2: Microvascular complications as function of different HGI groups

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Keywords: Microvascular complications, type 1 diabetes, CGM, HbA1c, HGI