Estimating HbA1c from average blood glucose - accuracy of estimates based on paediatric clinic data

Hanin Insyirah Mohd Amir, Vicky Alexander, Scott Graham, Leslie McKenzie, Heather Thom, Clare Webster, Nicholas Conway

Research output: Contribution to conferencePoster

Abstract

Introduction: HbA1c is an abstract concept that is poorly understood by children and young people (CYP). Average blood glucose (aBG) is readily available and is often used as a proxy for HbA1c when discussing glycemic control. Published models enable conversion of aBG to HbA1c, derived from adult cohorts in study conditions. There are a lack of studies validating these models with CYP in a clinical setting. This study aimed to compare estimated HbA1c (eHbA1c) obtained from aBG, with actual HbA1c in CYP with T1D attending a pediatric diabetes clinic.

Methods: HbA1c data were retrospectively extracted for all patients attending NHS Tayside pediatric diabetes clinic over 12 months (Jan18–Jan19). aBG was calculated from historical data for 3 months prior to each HbA1c measurement. aBG was converted to eHbA1c using Nathan et al’s equation. eHbA1c and actual HbA1c were compared using Pearson’s correlation. The difference between eHbA1c and actual HbA1c was analysed with respect to demographic predictors (age, diabetes duration, no. of BG checks/day) using multivariable linear regression.

Results: 165 patients had HbA1c measured during the study period. Of these, 60 patients had historical BG data. Mean age was 12.1 years (SD3.2), mean diabetes duration 5.7 years (SD3.2). Mean no. of BG checks/d was 3.8 (SD2.5,range 0.1-11.1). Mean aBG was 11.9mmol/l (SD3.2), mean actual HbA1c was 73mmol/mol (SD19). eHbA1c was highly correlated with actual HbA1c (r=0.677,p<0.001). Median difference between eHbA1c and actual HbA1c was 7 mmol/mol (IQR14). The optimum number of BG checks was 4-5/d - a lower number of BG checks/d was highly predictive of larger differences between eHbA1c and actual HbA1c (B-2.4,95%CI -3.6 to -1.2,p<0.001).

Conclusion: Conversion of aBG to eHbA1c would appear to be an accurate proxy for actual HbA1c in this pediatric cohort. Caution should be applied when interpreting eHbA1c if average number of BG checks is <4-5/d.
Original languageEnglish
Publication statusPublished - 30 Oct 2019
EventInternational Society for Pediatric and Adolescent Diabetes Conference 2019 - Boston, United States
Duration: 30 Oct 20191 Nov 2019
https://2019.ispad.org/

Conference

ConferenceInternational Society for Pediatric and Adolescent Diabetes Conference 2019
Abbreviated titleISPAD 2019
CountryUnited States
CityBoston
Period30/10/191/11/19
Internet address

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    Insyirah Mohd Amir, H., Alexander, V., Graham, S., McKenzie, L., Thom, H., Webster, C., & Conway, N. (2019). Estimating HbA1c from average blood glucose - accuracy of estimates based on paediatric clinic data. Poster session presented at International Society for Pediatric and Adolescent Diabetes Conference 2019, Boston, United States.