Role of random blood glucose and HbA1c levels in optimizing glucose tolerance screening in early pregnancy: a retrospective cohort study

Abstract

Objective: Random blood glucose (rBG) levels are commonly measured in Japan; however, no standardized cutoff values exist for glucose tolerance screening in early pregnancy. The contribution of glycated hemoglobin (HbA1c) and glycated albumin (GA) measurements to the diagnosis of gestational diabetes mellitus (GDM) remains unclear. Therefore, we aimed to evaluate the significance of these glycemic indicators in early pregnancy for predicting GDM.

Methods: This observational cohort study enrolled pregnant women who underwent initial prenatal examinations to determine their rBG, HbA1c, and GA levels at a rural maternity facility. Clinical data were retrospectively reviewed.

Results: A total of 449 patients were analyzed, comprising 394 with normal glucose tolerance (NGT) and 55 with GDM. The rBG, HbA1c, and GA levels were significantly higher during early pregnancy in women who developed GDM than in those with NGT. Receiver operating characteristic curve analysis revealed that the areas under the curve (AUC) for rBG, HbA1c, and GA were 0.733, 0.591, and 0.608, respectively, with cutoff values of 100 mg/dL, 5.2%, and 14.6%, respectively. These cutoff values had sensitivities of 52.7%, 70.9%, and 36.4% and specificities of 87.6%, 43.4%, and 82.5%, respectively. The product of rBG and HbA1c levels demonstrated improved performance, with an AUC of 0.750, cutoff value of 509, 63.6% sensitivity, and 83.5% specificity.

Conclusion: Glucose tolerance screening in early pregnancy using an rBG level of 100 mg/dL and an HbA1c level of 5.2% as cutoff values may help identify high-risk cases and enable early diagnosis of GDM.

Keywords: Gestational diabetes mellitus; Glycated albumin; Glycated hemoglobin; Normal glucose tolerance; Random blood glucose.

Fig. 1.

Blood glucose screening during pregnancy at our hospital. rBG, random blood glucose; HbA1c, glycated hemoglobin; GA, glycated albumin; 50gGCT, 50 g glucose challenge test; 75gOGTT, 75 g oral glucose tolerance test; GDM, gestational diabetes mellitus.

Fig. 2.

Patient flow diagram. rBG, random blood glucose; 50gGCT, 50 g glucose challenge test; DM, diabetes mellitus; 75gOGTT, 75 g oral glucose tolerance test; NGT, normal glucose tolerance; GDM, gestational diabetes mellitus.

Fig. 3.

Comparison of the results of blood glucose screening in early pregnancy between the NGT and GDM groups. (A) rBG, (B) HbA1c, (C) GA, (D) rBG×HbA1c, and (E) rBG×HbA1c×GA levels between 8 weeks and 13 weeks of gestation in the NGT (n=394) and GDM (n=55) groups. rBG, random blood glucose; NGT, normal glucose tolerance; GDM, gestational diabetes mellitus; HbA1c, glycated hemoglobin; GA, glycated albumin.

Fig. 4.

ROC analyses of the diagnostic and predictive accuracy of rBG, HbA1c, and GA levels for gestational diabetes mellitus. ROC curves for the prediction of gestational diabetes mellitus based on (A) rBG, (B) rBG×HbA1c, and (C) rBG×HbA1c×GA. The dots mean the optimal cutoff values. rBG, random blood glucose; HbA1c, glycated hemoglobin; GA, glycated albumin; ROC, receiver operating characteristic.

Fig. 5.

Physiological changes in glycemic markers and Hb during pregnancy in women with NGT. The levels of (A) rBG, (B) HbA1c, (C) GA, (D) GA/HbA1c ratio, and (E) Hb in first and third trimesters of pregnancy in women with NGT (n=394). rBG, random blood glucose; HbA1c, glycated hemoglobin; GA, glycated albumin; Hb, hemoglobin; NGT, normal glucose tolerance.