Evaluation of HbA1c from CGM traces in an Indian population

Front Endocrinol (Lausanne). 2023 Nov 20:14:1264072. doi: 10.3389/fendo.2023.1264072. eCollection 2023.

Abstract

Introduction: The development of continuous glucose monitoring (CGM) over the last decade has provided access to many consecutive glucose concentration measurements from patients. A standard method for estimating glycated hemoglobin (HbA1c), already established in the literature, is based on its relationship with the average blood glucose concentration (aBG). We showed that the estimates obtained using the standard method were not sufficiently reliable for an Indian population and suggested two new methods for estimating HbA1c.

Methods: Two datasets providing a total of 128 CGM and their corresponding HbA1c levels were received from two centers: Health Centre, Savitribai Phule Pune University, Pune and Joshi Hospital, Pune, from patients already diagnosed with diabetes, non-diabetes, and pre-diabetes. We filtered 112 data-sufficient CGM traces, of which 80 traces were used to construct two models using linear regression. The first model estimates HbA1c directly from the average interstitial fluid glucose concentration (aISF) of the CGM trace and the second model proceeds in two steps: first, aISF is scaled to aBG, and then aBG is converted to HbA1c via the Nathan model. Our models were tested on the remaining 32 data- sufficient traces. We also provided 95% confidence and prediction intervals for HbA1c estimates.

Results: The direct model (first model) for estimating HbA1c was HbA1cmmol/mol = 0.319 × aISFmg/dL + 16.73 and the adapted Nathan model (second model) for estimating HbA1c is HbA1cmmol/dL = 0.38 × (1.17 × ISFmg/dL) - 5.60.

Discussion: Our results show that the new equations are likely to provide better estimates of HbA1c levels than the standard model at the population level, which is especially suited for clinical epidemiology in Indian populations.

Keywords: average blood glucose concentration (aBG); average interstitial fluid glucose concentration (aISF); continuous glucose monitoring (CGM); glycated hemoglobin (HbA1c); type 2 diabetes (T2D).

MeSH terms

  • Blood Glucose
  • Blood Glucose Self-Monitoring / methods
  • Diabetes Mellitus, Type 1* / diagnosis
  • Diabetes Mellitus, Type 1* / epidemiology
  • Diabetes Mellitus, Type 2* / diagnosis
  • Diabetes Mellitus, Type 2* / epidemiology
  • Glycated Hemoglobin
  • Humans
  • India / epidemiology

Substances

  • Glycated Hemoglobin
  • Blood Glucose

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This work was financially supported by Rastriya Ucchattar Shiksha Abhiyan (RUSA CBS TH 4.3), Savitribai Phule Pune University, Pune. SK is a recipient of a Senior Research Fellowship from the Council of Scientific and Industrial Research (CSIR), India. SM is a Junior Research Fellow supported by a DST INSPIRE Fellowship, Department of Science and Technology, Government of India.