Achieving the HbA1c Target Requires Longer Time in Range in Pregnant Women With Type 1 Diabetes

Abstract

Aims Continuous glucose monitoring (CGM) overcomes the limitations of glycated hemoglobin (HbA1c). This study was to investigate the relationship between CGM metrics and laboratory HbA1c in pregnant women with type 1 diabetes. Methods An observational study enrolled pregnant women with type 1 diabetes who wore CGM devices during pregnancy and postpartum from 11 hospitals in China from January 2015 to June 2019. CGM data were collected to calculate time-in-range (TIR), time above range (TAR), time below range (TBR), and glycemic variability parameters. Relationships between the CGM metrics and HbA1c were explored. Linear and curvilinear regressions were conducted to investigate the best-fitting model to clarify the influence of HbA1c on the TIR-HbA1c relationship during pregnancy. Results A total of 272 CGM data and corresponding HbA1c from 98 pregnant women with type 1 diabetes and their clinical characteristics were analyzed in this study. Mean HbA1c and TIR were 6.49±1.29% and 76.16±17.97% during pregnancy, respectively. HbA1c was moderately correlated with TIR 3.5-7.8(R= -0.429, P=0.001), mean glucose (R= 0.405, P=0.001) and TAR 7.8 (R=0.435, P=0.001), but was weakly correlated with TBR 3.5 (R=0.034, P=0.001) during pregnancy. On average, a 1% (11 mmol/mol) decrease in HbA1c corresponded to an 8.5% increase in TIR 3.5-7.8. During pregnancy, HbA1c of 6.0%, 6.5% and 7.0% were equivalent to a TIR 3.5-7.8 of 78%, 74%, and 69%, respectively. Conclusions We found that there was a moderate correlation between HbA1c and TIR 3.5-7.8 during pregnancy. To achieve the HbA1c target <6.0%, pregnant women with type 1 diabetes should strive for TIR 3.5-7.8 >78% (18h 43min) during pregnancy.

Continuous glucose monitoring metrics (Mean Glucose, time above range and time in range) are superior to glycated haemoglobin for assessment of therapeutic efficacy

“…The present re‐analysis of data from published studies involving both T1D 9‐14,16 and T2D 15 led to several findings: HbA1c is only weakly correlated with Mean Glucose and other variables obtainable using CGM. %TIR is correlated with HbA1c and with Mean Glucose . Accordingly, %TIR could be used as a replacement or substitute for HbA1c in evaluation of clinical trials, real‐world data, and for management of individual subjects. %TAR had consistently higher correlations (magnitude) with HbA1c and with Mean Glucose than %TIR .…”

“…This is a consistent finding in studies of people with T1D and T2D (Figure 1). Errors in the estimates ( rms ) of Mean Glucose can be twofold smaller when using %TAR than when using %TIR 14‐16 The relationship of %TAR with Mean Glucose was linear.…”

“…We examined previously reported correlations among HbA1c , Mean Glucose , %TIR and %TAR for people with either type 1 (T1D) or type 2 diabetes (T2D) 9‐16 . We used data from four studies involving a total of 545 people with T1D 9‐13 which evaluated the effectiveness of an intervention involving use of real‐time CGM over a period of 6 months.…”

“…For CGM data obtained from people with T2D, where HbA1c values were not available, we examined correlations among Mean Glucose , %TAR and %TIR (Figure 1C). Results from another dataset during pregnancy and the postpartum period are shown in the Supplementary Materials 16 …”

“…This relationship is much weaker during pregnancy even when the target range is adjusted appropriately (63-140 mg/ dL) 16 but fairly comparable in the postpartum period (Figure S1 in Supplementary Materials). 16…”