A comparison of fasting plasma glucose and glucose challenge test for screening of gestational diabetes mellitus

Employing fasting plasma glucose to safely limit the use of oral glucose tolerance tests in pregnancy: a pooled analysis of four Norwegian studies

Background/objective

There is no international consensus about the optimal approach to screening and diagnosis of gestational diabetes mellitus (GDM). Fasting plasma glucose (FPG) has been proposed as an alternative universal screening test to simplify the diagnosis of GDM. We investigate the ability of the FPG to predict a 2-hour glucose value below the cut-off for GDM, thereby "ruling out" the necessity of a full OGTT and assess the proportion of GDM-related complications associated with the identified FPG level.

Materials and methods

This study included secondary data from four Norwegian pregnancy cohorts (2002-2013), encompassing 2960 women universally screened with late mid-pregnancy 75g OGTT measuring FPG and 2-hour glucose. For a range of FPG thresholds, we calculated sensitivity to predict elevated 2-hour glucose, number of OGTTs needed and percentage of GDM cases missed, applying modified World Health Organization (WHO) 2013 criteria (2013WHO) and 2017 Norwegian criteria (2017Norwegian). We analyzed pregnancy outcomes for women above and below our selected threshold.

Results

The prevalence of GDM was 16.6% (2013WHO) and 10.1% (2017Norwegian). A FPG threshold of 4.7 mmol/L had a sensitivity of 76% (2013WHO) and 80% (2017Norwegian) for detecting elevated 2-hour glucose, with few missed GDM cases (2.0% of those ruled out and 7.5% of all GDM cases for 2013WHO, and 1.1% of those ruled out and 7% of all GDM cases for 2017Norwegian). When excluding women with FPG <4.7mmol/l and those with GDM based on FPG, only 24% (2013WHO) and 29% (2017Norwegian) would require OGTT. Women with FPG <4.7mmol/l, including missed GDM cases, had low risk of large-for-gestational-age newborns, cesarean section and operative vaginal delivery.

Conclusion

A FPG threshold of 4.7mmol/l as a first step when screening for GDM could potentially eliminate the need for OGTT in 70-77% of pregnancies. Women with FPG below this threshold appear to carry low risk of GDM-associated adverse pregnancy outcomes.

Intermediate hyperglycemia in early pregnancy: A South Asian perspective

“Intermediate hyperglycemia in early pregnancy (IHEP)” refers to mild hyperglycemia detected before 24 gestational weeks (GW), satisfying the criteria for the diagnosis of gestational diabetes mellitus. Many professional bodies recommend routine screening for “overt diabetes” in early pregnancy, which identifies a significant number of women with mild hyperglycemia of undetermined significance. A literature search revealed that one-third of GDM women in South Asian countries are diagnosed before the conventional screening period of 24 GW to 28 GW; hence, they belong in the IHEP category. Most hospitals in this region diagnose IHEP by oral glucose tolerance test (OGTT) using the same criteria used for GDM diagnosis after 24 GW. There is some evidence to suggest that South Asian women with IHEP are more prone to adverse pregnancy events than women with a diagnosis of GDM after 24 GW, but this observation needs to be proven by randomized control trials. Fasting plasma glucose is a reliable screening test for GDM that can obviate the need for OGTT for GDM diagnosis among 50% of South Asian pregnant women. HbA1c in the first trimester predicts GDM in later pregnancy, but it is not a reliable test for IHEP diagnosis. There is evidence to suggest that HbA1c in the first trimester is an independent risk factor for several adverse pregnancy events. Further research to identify the patho-genetic mechanisms behind the fetal and maternal effects of IHEP is strongly recommended.

Screening for Gestational Diabetes: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Gestational diabetes is associated with several poor health outcomes.

OBJECTIVE

To update the 2012 review on screening for gestational diabetes to inform the US Preventive Services Task Force.

DATA SOURCES

MEDLINE, EMBASE, and CINAHL (2010 to May 2020), ClinicalTrials.gov, reference lists; surveillance through June 2021.

STUDY SELECTION

English-language intervention studies for screening and treatment; observational studies on screening; prospective studies on screening test accuracy.

DATA EXTRACTION AND SYNTHESIS

Dual review of titles/abstracts, full-text articles, and study quality. Single-reviewer data abstraction with verification. Random-effects meta-analysis or bivariate analysis (accuracy).

MAIN OUTCOMES AND MEASURES

Pregnancy, fetal/neonatal, and long-term health outcomes; harms of screening; accuracy.

RESULTS

A total of 76 studies were included (18 randomized clinical trials [RCTs] [n = 31 241], 2 nonrandomized intervention studies [n = 190], 56 observational studies [n = 261 678]). Direct evidence on benefits of screening vs no screening was limited to 4 observational studies with inconsistent findings and methodological limitations. Screening was not significantly associated with serious or long-term harm. In 5 RCTs (n = 25 772), 1-step (International Association of Diabetes and Pregnancy Study Group) vs 2-step (Carpenter and Coustan) screening was significantly associated with increased likelihood of gestational diabetes (11.5% vs 4.9%) but no improved health outcomes. At or after 24 weeks of gestation, oral glucose challenge tests with 140- and 135-mg/dL cutoffs had sensitivities of 82% and 93%, respectively, and specificities of 82% and 79%, respectively, against Carpenter and Coustan criteria, and a test with a 140-mg/dL cutoff had sensitivity of 85% and specificity of 81% against the National Diabetes Group Data criteria. Fasting plasma glucose tests with cutoffs of 85 and 90 mg/dL had sensitivities of 88% and 81% and specificities of 73% and 82%, respectively, against Carpenter and Coustan criteria. Based on 8 RCTs and 1 nonrandomized study (n = 3982), treatment was significantly associated with decreased risk of primary cesarean deliveries (relative risk [RR], 0.70 [95% CI, 0.54-0.91]; absolute risk difference [ARD], 5.3%), shoulder dystocia (RR, 0.42 [95% CI, 0.23-0.77]; ARD, 1.3%), macrosomia (RR, 0.53 [95% CI, 0.41-0.68]; ARD, 8.9%), large for gestational age (RR, 0.56 [95% CI, 0.47-0.66]; ARD, 8.4%), birth injuries (odds ratio, 0.33 [95% CI, 0.11-0.99]; ARD, 0.2%), and neonatal intensive care unit admissions (RR, 0.73 [95% CI, 0.53-0.99]; ARD, 2.0%). The association with reduction in preterm deliveries was not significant (RR, 0.75 [95% CI, 0.56-1.01]).

CONCLUSIONS AND RELEVANCE

Direct evidence on screening vs no screening remains limited. One- vs 2-step screening was not significantly associated with improved health outcomes. At or after 24 weeks of gestation, treatment of gestational diabetes was significantly associated with improved health outcomes.

Development of a fasting blood glucose-based strategy to diagnose women with gestational diabetes mellitus at increased risk of adverse outcomes in a COVID-19 environment

Objective

To evaluate the role of fasting blood glucose (FBG) to minimise the use of the oral glucose tolerance test in pregnancy (POGTT) for the diagnosis of gestational diabetes mellitus (GDM).

Research design and methods

We analysed the POGTTs of 26,242 pregnant women in Queensland, Australia, performed between 1 January 2015 and 30 June 2015. A receiver operator characteristics (ROC) assessment was undertaken to indicate the FBG level that most effectively identified women at low risk of an abnormal result.

Results

There were 3,946 (15.0%) patients having GDM with 2,262 (8.6%) having FBG ≥ 5.1mmol/l. The ROC identified FBG levels >4.6mmol/l having the best specificity (77%) and sensitivity (54%) for elevated 1 and/or 2hr BGLs. There were 19,321 (73.7%) women having FBG < 4.7mmol/l with a prevalence of GDM of 4.0%, less than 1/3^rd the overall rate. Only 4,638 (17.7%) women having FBGs from 4.7–5.0mmol/l would require further evaluation to confirm or exclude the diagnosis.

Conclusion

This contemporary study of women across the state of Queensland, Australia suggests the FBG can be used effectively to define glucose tolerance in pregnancy, minimising their contact with pathology laboratories and potential exposure to the corona virus. This analysis, used in conjunction with outcome data from the HAPO study, provides reassurance to women and their health professionals that FBG < 4.7mmol/l has both a low rate of abnormal glucose tolerance and minimal adverse pregnancy-associated complications.

Accuracy of screening tests for gestational diabetes mellitus in Southeast Asia: A systematic review of diagnostic test accuracy studies

BACKGROUND

To investigate the accuracy of screening tests for gestational diabetes mellitus (GDM) in Southeast Asian pregnant women.

METHODS

We searched PubMed (MEDLINE), Web of Science, Cochrane Library, ClinicalTrials.gov, Google Scholar, and Google for relevant articles published in English up to November 2018 using search terms related to GDM, screening tests for GDM and diagnostic performance. The studies were independently screened and selected by both authors. The methodological quality of the included studies was independently assessed by quality assessment of diagnostic accuracy studies 2. A hierarchical summary receiver operating characteristic (HSROC) model was created to estimate the HSROC curve. The summary sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were calculated in a meta-analysis using bivariate random-effects model.

RESULTS

A total of 19 studies were included in which the 100 g oral glucose tolerance test (OGTT) and 75 g OGTT were the two common reference standards for diagnosis of GDM. Most points of diagnostic performance in the HSROC 50 g GCT curve compared with the 100 g OGTT reference standard were clustered in the upper left-hand quadrant. The pooled sensitivity and specificity of the 50 g GCT were 79% (95% confidence interval [CI] 64%-89%) and 74% (95% CI 59%-85%), respectively. For the 75 g OGTT reference standard, the non-fasting 2-hour plasma glucose showed quite similar sensitivity the 50 g GCT compared with the 100 g OGTT reference standard. The pooled sensitivities and specificities of the fasting plasma glucose and hemoglobin A1c were 81% (95% CI 76%-86%) and 70% (95% CI 67%-72%), and 80% (95% CI 66%-90%) and 69% (95% CI 58%-78%), respectively.

CONCLUSION

Our findings indicate that the 50 g GCT using the threshold of 140 mg/dL is a good screening test for identifying GDM at 24 to 28 weeks' gestational age for both high-risk and universal screening strategies in Southeast Asian countries. The non-fasting 2-hour PG, fasting plasma glucose or hemoglobin A1c are alternative choices for screening.

Italian recommendations for the diagnosis of gestational diabetes during COVID-19 pandemic: Position statement of the Italian Association of Clinical Diabetologists (AMD) and the Italian Diabetes Society (SID), diabetes, and pregnancy study group

AIM

In response to the COVID-19 pandemic, there is a need for substantial changes in the procedures for accessing healthcare services. Even in the current pandemic, we should not reduce our attention towards the diagnosis and treatment of GDM. The purpose of this document is to provide a temporary guide for GDM screening, replacing the current guidelines when it is not possible to implement standard GDM screening because of an unfavorable risk/benefit ratio for pregnant women or when usual laboratory facilities are not available.

DATA SYNTHESIS

At the first visit during pregnancy, we must exclude the presence of "Overt diabetes" in all women. The criteria for the diagnosis of overt diabetes are either fasting plasma glucose ≥126 mg/dL, or random plasma glucose ≥200 mg/dL, or glycated hemoglobin ≥6.5%. When the screening procedure (OGTT) cannot be safely performed, the diagnosis of GDM is acceptable if fasting plasma glucose is ≥ 92 mg/dL. In order to consider the impaired fasting glucose as an acceptable surrogate for the diagnosis of GDM, the fasting glucose measurement should be performed within the recommended time windows for the risk level (high or medium risk).

CONCLUSIONS

The changes to the screening procedure for GDM reported below are specifically produced in response to the health emergency of the COVID-19 pandemic. Therefore, these recommended changes should cease to be in effect and should be replaced by current national guidelines when the healthcare authorities declare the end of this emergency.

Simplifying the screening of gestational diabetes by maternal age plus fasting plasma glucose at first prenatal visit: A prospective cohort study

AIM

The addition of maternal age to fasting plasma glucose (FPG) at 24-28 gestational weeks improves the performance of GDM screening as maternal age increases. However, this method delays the diagnosis of GDM. Since FPG at the first prenatal visit (FPV) is a screening option for pre-existing diabetes, we evaluated the performance of age plus FPG at the FPV to reduce the need for the OGTT.

METHODS

Pregnant women were recruited consecutively in 2013-2018 (the training cohort) and 2019 (the validation cohort). We excluded women with twin pregnancies, unavailable FPG at the FPV or OGTT data, pre-pregnancy diabetes, or a history of GDM. All participants underwent FPG and haemoglobin A1c (HbA1c) at the FPV and received 75-g OGTT at 24-28 gestational weeks if FPG at the FPV was <92 mg/dL. GDM was diagnosed by the IADPSG criteria. Two algorithms were developed with the cutoffs determined when the percentage requiring OGTT (OGTT%) was the lowest and the sensitivity was ≥90%.

RESULTS

The incidence of GDM increased with age. The "FPG at the FPV" algorithm reduced OGTT% to 68.8% with the FPG cutoff at 79 mg/dl. The "age plus FPG at the FPV" algorithm, with the cutoff of 114, further reduced OGTT% to 58.3%, with the sensitivity of 90.7% (9.3% GDM missed) and the specificity of 100%. These findings were replicated in the validation cohort.

CONCLUSIONS

Screening GDM by maternal age plus FPG at the FPV can reduce OGTT%, especially in populations with a significant proportion of pregnant women with advanced ages.

The post-HAPO situation with gestational diabetes: the bright and dark sides

AIM

In 2010, in light of the data coming from the HAPO study, the International Association of Diabetes and Pregnancy Study Groups (IADPSG) proposed a new detection strategy and diagnostic criteria for gestational diabetes based on a one-step approach with a 75 g OGTT. This review analyzes and discusses the bright and dark sides of their application.

METHODS

The assessment of these recommendations by the international organizations involved in the care of gestational diabetes and a series of observational, retrospective and prospective studies that have been published since 2010 regarding the use of the IADPSG recommendations have been evaluated.

RESULTS

The different international associations involved in the care of pregnancy and of pregnancy complicated by diabetes have not taken an univocal position some of which have accepted them, while others have criticized them. Then, the actual application of the approach recommended by the IADPSG for detecting and diagnosing GDM varies, even at centers that reportedly accept the new diagnostic criteria.

CONCLUSION

So the challenge lies in making every effort to achieve a global standardization of the strategies for detecting, diagnosing and treating GDM.

Characteristics of different risk factors and fasting plasma glucose for identifying GDM when using IADPSG criteria: a cross-sectional study

Background

The Swedish National Board of Health and Welfare (SNBHW) recommended the new diagnostic criteria for GDM based upon Hyperglycaemia and Adverse Pregnancy Outcomes (HAPO) study thresholds. Due to limited knowledge base, no recommendations were made on GDM screening. The aim of this study is to evaluate test characteristics of risk factors and fasting blood glucose as screening tests for diagnosing GDM using diagnostic thresholds based upon HAPO study 1.75/2.0 (model I/II respectively) odds ratio for adverse pregnancy outcomes.

Methods

This cross-sectional, population-based study included all pregnant women who attended maternal health care in Örebro County, Sweden between the years 1994–96. A 75 g OGTT with capillary fasting and 2-h blood glucose was offered to all pregnant women at week 28–32. Risk factors and repeated random glucose samples were collected. Sensitivity, specificity and predictive values of blood glucose were calculated.

Results

Prevalence of GDM was 11.7% with model I and 7.2% with the model II criteria. Risk factors showed 28%, (95% CI 24–32) and 31%, (95% CI 25–37) sensitivity for model I and II respectively. A fasting cut off ≥4.8 mmol/l occurred in 24% of women with 91%, (95% CI 88–94) sensitivity and 85%, (95% CI 83–86) specificity using model I while a fasting cut off ≥5.0 mmol/l occurred in 14% with 91%, (95% CI 87–94) sensitivity and 92%, (95% CI 91–93) specificity using model II.

Conclusion

Risk factor screening for GDM was found to be poorly predictive of GDM but fasting glucose of 4.8–5.0 mmol/l showed good test characteristics irrespective of diagnostic model and results in a low rate of OGTTs.

Single Fasting Plasma Glucose Versus 75-g Oral Glucose-Tolerance Test in Prediction of Adverse Perinatal Outcomes: A Cohort Study

Background

There remains uncertainty regarding whether a single fasting glucose measurement is sufficient to predict risk of adverse perinatal outcomes.

Methods

We included 12,594 pregnant women who underwent a 75-g oral glucose-tolerance test (OGTT) at 22–28 weeks' gestation in the Born in Guangzhou Cohort Study, China. Outcomes were large for gestational age (LGA) baby, cesarean section, and spontaneous preterm birth. We calculated the area under the receiver operator characteristic curves (AUCs) to assess the capacity of OGTT glucose values to predict adverse outcomes, and compared the AUCs of different components of OGTT.

Results

1325 women had a LGA baby (10.5%). Glucose measurements were linearly associated with LGA, with strongest associations for fasting glucose (odds ratio 1.37, 95% confidence interval 1.30–1.45). Weaker associations were observed for cesarean section and spontaneous preterm birth. Fasting glucose have a comparable discriminative power for prediction of LGA to the combination of fasting, 1 h, and 2 h glucose values during OGTT (AUCs, 0.611 vs. 0.614, P = 0.166). The LGA risk was consistently increased in women with abnormal fasting glucose (≥ 5.1 mmol/l), irrespective of 1 h or 2 h glucose levels.

Conclusions

A single fasting glucose measurement performs comparably to 75-g OGTT in predicting risk of having a LGA baby.

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Fasting glucose had a significantly stronger association with large for gestational age than post-load glucoses.

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Single fasting glucose has comparable predictive ability of large for gestational age to 75g OGTT.

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Single fasting glucose test can be an alternative for identifying high risk of large for gestational age in Chinese women.

The new criteria for gestational diabetes (GDM) screening and diagnosis suggests that single abnormal of a fasting, 1 h or 2 h glucose measured by an universal, single-stage screening of 2 h 75-g oral glucose-tolerance test (OGTT) is adequate to make a diagnosis. However, the utility of each glucose measurement in the prediction of poor perinatal outcomes was unclear. Here, we reported single fasting plasma glucose performs comparably to 75 g OGTT in identification of women at increased risk of delivering a large for gestational age baby. Single fasting glucose testing can be an alternative for GDM screening, which will substantially reduce the psychological impact, opportunity and direct health costs for women and their families.

Gestational diabetes mellitus: Screening with fasting plasma glucose

Fasting plasma glucose (FPG) as a screening test for gestational diabetes mellitus (GDM) has had a checkered history. During the last three decades, a few initial anecdotal reports have given way to the recent well-conducted studies. This review: (1) traces the history; (2) weighs the advantages and disadvantages; (3) addresses the significance in early pregnancy; (4) underscores the benefits after delivery; and (5) emphasizes the cost savings of using the FPG in the screening of GDM. It also highlights the utility of fasting capillary glucose and stresses the value of the FPG in circumventing the cumbersome oral glucose tolerance test. An understanding of all the caveats is crucial to be able to use the FPG for investigating glucose intolerance in pregnancy. Thus, all health professionals can use the patient-friendly FPG to simplify the onerous algorithms available for the screening and diagnosis of GDM - thereby helping each and every pregnant woman.

Utility of Pregestational Body Mass Index and Initial Fasting Plasma Glucose in Predicting Gestational Diabetes Mellitus

OBJECTIVE

The present study aimed to evaluate the pregestational body mass index (preBMI) and initial fasting plasma glucose (FPG) in predicting gestational diabetes mellitus (GDM) in southern Chinese women.

STUDY DESIGN

A total of 327 pregnant women were recruited from the third affiliated hospital of Sun Yat-Sen University, Guangzhou, China. The preBMI and initial FPG at 16-18 weeks' gestation were measured. Oral glucose tolerance test was performed at 24-28 weeks' gestation. The sensitivity and specificity of preBMI and initial FPG as predictors for GDM were evaluated by receiver-operator characteristic curve analysis.

RESULTS

Both preBMI and initial FPG correlated with the 0-hour, 1-hour and 2-hour plasma glucose during oral glucose tolerance test (P < 0.05). The area under receiver-operator characteristic curve was 0.63 (95% CI: 0.57-0.68) for preBMI and 0.68 (95% CI: 0.61-0.72) for initial FPG in diagnosing GDM. The optimal cutoff for preBMI was 21.5 kg/m(2) (sensitivity 52.1% and specificity 69.2%) and 4.6 mmol/L (sensitivity 64.6% and specificity 65.2%) for initial FPG. Interestingly, the initial FPG had a better sensitivity compared to preBMI when the specificity was the same. Multivariate logistic regression analysis showed that initial FPG but not preBMI was the independent risk factor for the later development of GDM. After adjustment for the preBMI and the maternal age, the odds ratios of initial FPG and parity were 3.57 (95% CI: 1.72-7.45) and 2.11 (95% CI: 1.20-3.72).

CONCLUSIONS

Although both preBMI and initial FPG could be used as indicators for GDM, the initial FPG may be more suitable for predicting GDM in southern Chinese women.

Screening and management of gestational diabetes

Gestational diabetes (GDM) is a frequent medical condition during pregnancy. It is associated with an increased risk of complications for both the mother and the baby during pregnancy and post partum. The International Association of Diabetes and Pregnancy Study Groups (IADPSG) has proposed a new screening strategy for overt diabetes in pregnancy and screening for GDM. However, there is still a lack of international uniformity in the approach to the screening and diagnosis of GDM. Controversies include universal versus selective screening, the optimal time for screening, appropriate tests and cutoff values, and whether testing should be conducted in one or two steps. This review gives an update on screening for GDM and overt diabetes during pregnancy. We also give an overview on the medical and obstetrical management of GDM.