Contribution of glucose variability to HbA1c levels in patients with type 1 diabetes

Luis Cardoso; Carla Batista; Dircea Rodrigues; Carolina Moreno; Daniela Guelho; Nuno Vicente; Margarida Balsa; Diana Martins; Diana Oliveira; Francisco Carrilho

doi:10.1530/endoabs.37.EP388

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Endocrine Abstracts (2015) 37 EP388 | DOI: 10.1530/endoabs.37.EP388

ECE2015 Eposter Presentations Diabetes (pathiophysiology & epitemiology) (80 abstracts)

Contribution of glucose variability to HbA1c levels in patients with type 1 diabetes

Luis Cardoso ¹ , Carla Batista ¹ , Dírcea Rodrigues ^1, , Carolina Moreno ^1, , Daniela Guelho ¹ , Nuno Vicente ¹ , Margarida Balsa ³ , Diana Martins ¹ , Diana Oliveira ¹ & Francisco Carrilho ¹

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¹Department of Endocrinology, Diabetes and Metabolism, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal; ²Faculty of Medicine, University of Coimbra, Coimbra, Portugal; ³Department of Endocrinology, Centro Hospitalar do Baixo Vouga, Aveiro, Portugal.

Background: Optimal management of type 1 diabetes requires full understanding of the relationships between the triad: HbA1c, fasting plasma glucose, and glucose variability (GV). As GV may contribute to HbA1c we assessed the influence of GV in HbA1c levels.

Research design and methods: We retrospectively analysed 9393 h of continuous glucose monitorings (CGMs) from 61 patients with type 1 diabetes. Periods of 24 h with missing values were excluded. We calculated various measures of GV and used a regression model to determine the impact of each GV measure to HbA1c level. GV was calculated using EasyGV Software and CGMs were recorded using iPro2 (Medtronic, Northridge, CA, USA).

Results: A total of 9393 h of CGM were analysed. Mean duration of diabetes was 17.7±9.6 years and HbA1c was 7.9±1.1%. S.D., continuous overlapping net glycaemic action (CONGA), mean absolute glucose (MAG), and mean of daily differences (MODD), were positively correlated with HbA1c (correlation coefficient of 0.26, 0.37, 0.26, and 0.33, respectively, all P<0.05), and all measures of GV were significantly higher for higher values of HbA1c (<7, 7–8, 8–9, and >9%, all P<0.05). Intraday GV measures contributed to 4–16% of HbA1c (S.D.: 10.2%, CONGA: 15.7%, mean amplitude of glycemic excursions (MAGE–CGM) 3.9%, and MAG 8.1%, P<0.05). Interday variability, measured by MODD, accounted for 13.1% of HbA1c. Furthermore, MODD was positively correlated with measures of quality of glycemic control, like glycemic risk assessment in diabetes equation (GRADE) score, J-index, high blood glucose index (HBGI), M-value, and average daily risk ratio (ADDR) (correlation coefficient of 0.41, 0.54, 0.57, 0.54, and 0.80, respectively, all P<0.05).

Conclusion: GV contributes significantly to HbA1c levels. This effect is more pronounced at higher HbA1c levels. Interday variability was the most important contributor to HbA1c. GV impairs significantly the quality of glycemic control of type 1 diabetic patients.