Hemoglobin A1c and Early Gestational Diabetes

First-trimester HbA1c in relation to plasma glucose concentrations in an oral glucose tolerance test at 12 to 16 weeks' gestation-a population-based study

BACKGROUND

Early-onset GDM often requires pharmacological treatment and is associated with adverse perinatal outcomes, but data is insufficient regarding the best methods to identify high-risk women requiring early GDM screening. The aim of this study was to analyze the diagnostic accuracy of HbA1c in the prediction of (1) plasma glucose concentrations > 90th percentile in an oral glucose tolerance test (OGTT) at 12-16 weeks' gestation; and (2) pharmacologically treated early- or late-onset GDM.

METHODS

HbA1c was measured at 8-14 weeks' gestation in a population-based cohort of 1394 Finnish women recruited for the Early Diagnosis of Diabetes in Pregnancy (EDDIE) study between 3/2013 and 12/2016. Information on maternal risk factors were collected at recruitment. Subsequently, a 2-hour 75 g OGTT was performed at 12-16 weeks' gestation (OGTT1), and if normal, repeated at 24-28 weeks' gestation (OGTT2). Early- and late-onset GDM were diagnosed using the same nationally endorsed cut-offs for fasting, 1 h- and 2 h-plasma glucose: ≥5.3, ≥ 10.0mmol/l, and/or ≥ 8.6mmol/l, respectively. In total, 52/1394 (3.7%) women required metformin or insulin treatment for GDM, including 39 women with early-onset GDM diagnosed at OGTT1 and 13 women with late-onset GDM diagnosed at OGTT2.

RESULTS

Maternal early-pregnancy HbA1c ≥ 35mmol/mol (≥ 5.4%) was the best cut-off to predict fasting or post-load plasma glucose > 90th percentile in OGTT1, but its diagnostic accuracy was low [AUC (95% CI) 0.65 (0.62 to 0.69), sensitivity 0.55 (0.49 to 0.60) and specificity 0.67 (0.64 to 0.70)] both alone and in combination with other maternal risk factors. However, HbA1c ≥ 35mmol/mol correlated positively with plasma glucose concentrations at all time points of OGTT1 and predicted pharmacologically treated GDM diagnosed at OGTT1 or OGTT2; AUC (95% CI) 0.75 (0.68 to 0.81), sensitivity 0.75 (0.61 to 0.86), specificity 0.64 (0.61 to 0.66).

CONCLUSIONS

In our population-based cohort, early-pregnancy HbA1c ≥ 35mmol/mol was positively associated with fasting and post-load plasma glucose concentrations in an OGTT at 12-16 weeks' gestation and predicted pharmacologically-treated early- and late-onset GDM, suggesting potential utility in first-trimester identification of women at high risk of severe GDM subtypes.

Trends in Screening for Diabetes in Early Pregnancy in the United States

Objective: The aim of this study was to characterize current diabetes screening practices in the first trimester of pregnancy in the United States, evaluate patient characteristics and risk factors associated with early diabetes screening, and compare perinatal outcomes by early diabetes screening. Methods: This was a retrospective cohort study of US medical claims data of persons diagnosed with a viable intrauterine pregnancy and who presented for care with private insurance before 14 weeks of gestation, without pre-existing pregestational diabetes, from the IBM MarketScan® database for the period January 1, 2016, to December 31, 2018. Univariate and multivariate analyses were used to evaluate perinatal outcomes. Results: A total of 400,588 pregnancies were identified as eligible for inclusion, with 18.0% of persons receiving early screening for diabetes. Of those with laboratory order claims, 53.1% underwent hemoglobin A1c testing, 30.0% underwent fasting glucose testing, and 16.9% underwent oral glucose tolerance testing. Compared with those who did not undergo early diabetes screening, those who did were more likely to be older; obese; having a history of gestational diabetes, chronic hypertension, polycystic ovarian syndrome, or hyperlipidemia; and having a family history of diabetes. In adjusted logistic regression, history of gestational diabetes (adjusted odds ratio 3.99; 95% confidence interval 3.73-4.26) had the strongest association with early diabetes screening. Adverse perinatal outcomes, including a higher rate of cesarean delivery, preterm delivery, preeclampsia, and gestational diabetes, occurred more frequently among women who underwent early diabetes screening. Conclusions: First-trimester early diabetes screening was mostly commonly performed by hemoglobin A1c evaluation, and persons who underwent early diabetes screening were more likely to experience adverse perinatal outcomes.

Association Between Social Vulnerability and Achieving Glycemic Control Among Pregnant Individuals With Pregestational Diabetes

OBJECTIVE

To evaluate the association between community-level social vulnerability and achieving glycemic control (defined as hemoglobin A1c [Hb A1c] less than 6.0% or less than 6.5%) among individuals with pregestational diabetes.

METHODS

We conducted a retrospective cohort of individuals with pregestational diabetes with singleton gestations from 2012 to 2016 at a tertiary care center. Addresses were geocoded using ArcGIS and then linked at the census tract to the Centers for Disease Control and Prevention's 2018 SVI (Social Vulnerability Index), which incorporates 15 Census variables to produce a composite score and four scores across thematic domains (socioeconomic status, household composition and disability, minority status and language, and housing type and transportation). Scores range from 0 to 1, with higher values indicating greater community-level social vulnerability. The primary outcome was Hb A1c less than 6.0%, and, secondarily, Hb A1c less than 6.5%, in the second or third trimesters. Multivariable Poisson regression with robust error variance was used to evaluate the association between SVI score as a continuous measure and target Hb A1c.

RESULTS

Among 418 assessed pregnant individuals (33.0% type 1; 67.0% type 2 diabetes), 41.4% (173/418) achieved Hb A1c less than 6.0%, and 56.7% (237/418) Hb A1c less than 6.5% at a mean gestational age of 29.5 weeks (SD 5.78). Pregnant individuals with a higher SVI score were less likely to achieve Hb A1c less than 6.0% compared with those with a lower SVI score. For each 0.1-unit increase in SVI score, the risk of achieving Hb A1c less than 6.0% decreased by nearly 50% (adjusted risk ratio [aRR] 0.53; 95% CI 0.36-0.77), and by more than 30% for Hb A1c less than 6.5% (adjusted odds ratio 0.67; 95% CI 0.51-0.88). With regard to specific SVI domains, those who scored higher on socioeconomic status (aRR 0.50; 95% CI 0.35-0.71) as well as on household composition and disability (aRR 0.55; 95% CI 0.38-0.79) were less likely to achieve Hb A1c less than 6.0%.

CONCLUSION

Pregnant individuals with pregestational diabetes living in an area with higher social vulnerability were less likely to achieve glycemic control, as measured by HgbA1c levels. Interventions are needed to assess whether addressing social determinants of health can improve glycemic control in pregnancy.

Improved gestational diabetes screening protocol

Objectives

This work aimed to assess the diagnostic validity of two approaches for the screening of gestational diabetes mellitus (GDM) with less discomfort for pregnant women.

Methods

A prospective diagnostic validation study was conducted with 2007 pregnant women. According to risk factors for GDM, women were classified into high-risk and low-risk groups. The current diagnostic procedure, based on oral glucose overload, was followed; simultaneously HbA_1c was tested and an algorithm combining both biomarkers was applied.

Results

In the low-risk group, the Glucose challenge test (GCT) showed a higher area under the curve (AUC 0.953; 95% CI 0.915-0.992) than the HbA_1c test (0.688; 95% CI 0.541-0.834). The best GCT cut-off, 153.5 mg/dL (8.52 mmol/L), showed higher diagnostic validity than that for HbA_1c, 28 mmol/mol (4.75%), and that the algorithm using both tests. In the high-risk group, the GCT showed better diagnostic performance than the HbA_1c and the algorithm; the optimal GCT cut-offs were higher than those recommended in current protocols. 13th week: GCT AUC 0.882 (95% CI 0.843-0.921), HbA_1c AUC 0.624 (95% CI 0.562-0.686), GCT cut-off 140.5 mg/dL (7.8 mmol/L), HbA_1c cut-off 33 mmol/mol (5.15%). 24th week: GCT AUC 0.944 (95% CI 0.925-0.962), HbA_1c AUC 0.642 (95% CI 0.575-0.709), GCT cut-off, 145.5 mg/dL (8.08 mmol/L), HbA_1c cut-off 29 mmol/mol (4.85%).

Conclusions

The GDM diagnostic approach using as the first step the GCT with higher cut-offs showed the best diagnostic validity. Applying these thresholds, 55.6 and 13.7% of 100 g. Oral glucose overloads would have been avoided in low-risk and high-risk pregnant women.