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Diabetologia. 2017 Apr;60(4):618-624. doi: 10.1007/s00125-017-4205-7. Epub 2017 Jan 19.

Translating HbA1c measurements into estimated average glucose values in pregnant women with diabetes.

Author information

1
School of Health and Social Care, University of Lincoln, Lincoln, UK.
2
Division of Epidemiology and Biostatistics, Leeds Institute of Cardiovascular and Metabolic Medicine, Clarendon Way, University of Leeds, Leeds, LS2 9JT, UK.
3
Institute for Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
4
Elsie Bertram Diabetes Centre, Norfolk and Norwich University Hospital NHS Trust, Norwich, UK.
5
Newcastle University Medicine Malaysia, Johor, Malaysia.
6
Norwich Medical School, University of East Anglia, Norwich, UK.
7
Division of Epidemiology and Biostatistics, Leeds Institute of Cardiovascular and Metabolic Medicine, Clarendon Way, University of Leeds, Leeds, LS2 9JT, UK. e.m.scott@leeds.ac.uk.

Abstract

AIMS/HYPOTHESIS:

This study aimed to examine the relationship between average glucose levels, assessed by continuous glucose monitoring (CGM), and HbA1c levels in pregnant women with diabetes to determine whether calculations of standard estimated average glucose (eAG) levels from HbA1c measurements are applicable to pregnant women with diabetes.

METHODS:

CGM data from 117 pregnant women (89 women with type 1 diabetes; 28 women with type 2 diabetes) were analysed. Average glucose levels were calculated from 5-7 day CGM profiles (mean 1275 glucose values per profile) and paired with a corresponding (±1 week) HbA1c measure. In total, 688 average glucose-HbA1c pairs were obtained across pregnancy (mean six pairs per participant). Average glucose level was used as the dependent variable in a regression model. Covariates were gestational week, study centre and HbA1c.

RESULTS:

There was a strong association between HbA1c and average glucose values in pregnancy (coefficient 0.67 [95% CI 0.57, 0.78]), i.e. a 1% (11 mmol/mol) difference in HbA1c corresponded to a 0.67 mmol/l difference in average glucose. The random effects model that included gestational week as a curvilinear (quadratic) covariate fitted best, allowing calculation of a pregnancy-specific eAG (PeAG). This showed that an HbA1c of 8.0% (64 mmol/mol) gave a PeAG of 7.4-7.7 mmol/l (depending on gestational week), compared with a standard eAG of 10.2 mmol/l. The PeAG associated with maintaining an HbA1c level of 6.0% (42 mmol/mol) during pregnancy was between 6.4 and 6.7 mmol/l, depending on gestational week.

CONCLUSIONS/INTERPRETATION:

The HbA1c-average glucose relationship is altered by pregnancy. Routinely generated standard eAG values do not account for this difference between pregnant and non-pregnant individuals and, thus, should not be used during pregnancy. Instead, the PeAG values deduced in the current study are recommended for antenatal clinical care.

KEYWORDS:

Average glucose; Continuous glucose monitoring; Estimated average glucose; Gestation; HbA1c; Pregnant; Type 1 diabetes; Type 2 diabetes

PMID:
28105519
PMCID:
PMC6518090
DOI:
10.1007/s00125-017-4205-7
[Indexed for MEDLINE]
Free PMC Article

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