How reliable is the fifty-gram, one-hour glucose screening test?

Resolving the Gestational Diabetes Diagnosis Conundrum: The Need for a Randomized Controlled Trial of Treatment

The diagnosis of and criteria for gestational diabetes mellitus (GDM) continue to divide the scientific and medical community, both between and within countries. Many argue for universal adoption of the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria and feel that further clinical trials are unjustified and even unethical. However, there are concerns about the large increase in number of women who would be diagnosed with GDM using these criteria and the subsequent impact on health care resources and the individual. This Perspective reviews the origins of the IADPSG consensus and points out some of its less well-known limitations, particularly with respect to identifying women at risk for an adverse pregnancy outcome. It also questions the clinical and cost-effectiveness data often cited to support the IADPSG glycemic thresholds. We present the argument that adoption of diagnostic criteria defining GDM should be based on response to treatment at different diagnostic thresholds of maternal glycemia. This will likely require an international multicenter trial of treatment.

Is Afamin a novel biomarker for gestational diabetes mellitus? A pilot study

BACKGROUND

In search of potential early biomarkers for timely prediction of gestational diabetes mellitus (GDM), we focused on afamin, a vitamin E-binding protein in human plasma.. Afamin plays a role in anti-apoptotic cellular processes related to oxidative stress and is associated with insulin resistance and other features of metabolic syndrome. During uncomplicated pregnancy its serum concentrations increase linearly. The aim of this study was to investigate the suitability of afamin as early marker for predicting GDM.

METHODS

In a first-trimester cohort from a prospective observational study of adverse pregnancy outcomes we secondarily analyzed afamin concentrations in 59 patients diagnosed with GDM and 51 controls. Additionally, afamin concentrations were cross-sectionally examined in a mid-trimester cohort of 105 women and compared with results from a simultaneously performed oral glucose tolerance test (OGTT). Subgroup analysis comparing patients treated with either insulin (iGDM) or dietary intervention (dGDM) was performed in both cohorts. Patients were recruited at the University Hospital Essen, Germany, between 2003 and 2016.

RESULTS

Results were adjusted for body-mass-index (BMI) and gestational age. First and mid-trimester cohorts yielded significantly elevated afamin concentrations in patients with pathological OGTT compared to patients without GDM (first trimester cohort: mean, 113.4 mg/l; 95% CI, 106.4-120.5 mg/l and 87.2 mg/l; 95% CI, 79.7-94.7 mg/l; mid-trimester cohort: mean, 182.9 mg/l; 95% CI, 169.6-196.2 mg/l and 157.3 mg/l; 95% CI, 149.1-165.4 mg/l, respectively). In the first-trimester cohort, patients developing iGDM later in pregnancy presented with significantly higher afamin concentrations compared to patients developing dGDM and compared to patients without GDM. In the mid-trimester cohort, mean concentrations of afamin differed significantly between patients with dGDM compared to controls and between patients with iGDM and controls. Patients with iGDM showed only slightly higher afamin levels compared to patients with dGDM.

CONCLUSION

Afamin may serve as a new early biomarker for pathological glucose metabolism during pregnancy. Further research is needed to determine afamin's concentrations during pregnancy, its predictive value for early detection of pregnancies at high risk to develop GDM and its diagnostic role during the second trimester.

Screening and diagnosis of gestational diabetes mellitus - relevance to low and middle income countries

Gestational diabetes mellitus (GDM) is one of the most common metabolic complications of pregnancy. Ever since the first systematic evaluation of the oral glucose tolerance test by O'Sullivan and colleagues was carried out in 1964, there has been controversy with respect to the optimal screening and diagnostic criteria to detect GDM. The recently proposed International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria for GDM has found fairly widespread acceptance, but it is still debated by several societies. This review intends to provide an overview of the evolution of the screening and diagnostic criteria for GDM. Debatable issues regarding optimal screening strategies, especially in the low resource settings of low and middle income countries are highlighted. The recent Women in India with GDM Strategy (WINGS) project carried out in Chennai, India tried to develop a Model of Care for GDM suitable for resource constrained settings. The findings related to screening and diagnosis of GDM based on WINGS are also highlighted in this review. Based on the WINGS experience we believe that despite the constraints in low and middle income countries at the present time, the IADPSG criteria appears to be the best. This will also help to bring out a uniform criteria for screening and diagnosis of GDM worldwide.

Comparative Study of Fasting Plasma Glucose Concentration and Glucose Challenge Test for Screening Gestational Diabetes Mellitus

Background

To compare the sensitivity and specificity of fasting plasma glucose (FPG) with that of standard glucose challenge test (GCT).

Materials and methods

Eighty-nine eligible pregnant women underwent GCT between 24th and 28th gestational week, followed by a diagnostic 3 hours 100 gm oral glucose tolerance test within 1 week. Out patient clinic in Father Muller Medical College Hospital, Mangalore. Data was analyzed for significance by chi-square test.

Results

Fasting plasma glucose concentration at a threshold value of 90 mg/dl and GCT at recommended standard threshold of 140 mg/dl yielded sensitivities of 66.7% and 100% respectively and specificities of 87.3% and 46.5% respectively. Reducing the threshold value of FPG to 80 mg/dl increased the sensitivity of test to 91.7% with specificity of 54.9% which was comparable to standard GCT, in our study.

Conclusion

Measuring FPG concentration using a cut-off of. 80 mg/dl is an easier, tolerable and more cost effective procedure than GCT for detecting more severe cases of GDM, i.e. the diabetes mellitus group. In resource poor settings with population belonging to average risk or high risk category, FPG at a cut-off of 90 mg/dl can be used to screen GDM.

How to cite this article

Sham S, Bhat BPR, Kamath A. Comparative Study of Fasting Plasma Glucose Concentration and Glucose Challenge Test for Screening Gestational Diabetes Mellitus. J South Asian Feder Obst Gynae 2014;6(2):75-78.

Fasting capillary glucose as a screening test for gestational diabetes mellitus

OBJECTIVE

To evaluate fasting capillary glucose as a screening test for gestational diabetes mellitus (GDM) compared with traditional risk factors and repeated random capillary glucose measurements.

DESIGN

Cross-sectional, population-based study.

SETTING

Maternal Health Care Clinics in Orebro County, Sweden.

POPULATION

An unselected population of women without diabetes.

METHODS

Fasting capillary glucose levels were measured at gestational weeks 28-32. Random capillary glucose levels were measured four to six times during pregnancy. Traditional risk factors for GDM were registered. GDM was diagnosed using a 75-g oral glucose tolerance test.

MAIN OUTCOME MEASURES

Sensitivity, specificity, likelihood ratios.

RESULTS

In 55 of 3616 women participating in the study, GDM was diagnosed before 34 weeks of gestation. For fasting capillary glucose cutoff values between 4.0 and 5.0 mmol/l, sensitivity was in the range between 87 and 47% and specificity between 51 and 96%. Using a combined screening model of traditional risk factors with fasting capillary glucose at various cutoff values increased the sensitivity only slightly compared with using fasting capillary glucose alone.

CONCLUSION

In this Swedish, unselected, low-risk population, fasting capillary glucose measurements were found to be an acceptable and useful screening test for GDM.

Screening for gestational diabetes mellitus in southern Asian women

AIM

To compare fasting plasma glucose (FPG) against 2-h postprandial plasma glucose (PPPG), following a carbohydrate meal, for screening of gestational diabetes mellitus (GDM) in southern Asian women with one or more risk factors.

METHODS

A comparative study was conducted at a university obstetric unit in Sri Lanka. Two hundred and seventy one women undergoing oral glucose tolerance test (OGTT) according to the WHO criteria of 1999 had a 2-h PPPG performed within the following week. Sensitivity, specificity, predictive values and correlation coefficients for predicting a diagnosis of GDM and areas under receiver-operator curves (ROC) were calculated for FPG and PPPG. The ability to predict GDM and to reduce the need for OGTT were the main outcome measures.

RESULTS

The mean period of gestation was 26.43 weeks (SD = 5.4) Seventy-five (27.7%) women were diagnosed with GDM. The optimal threshold for FPG was 4.4 mmol/L and for PPPG 4.7 mmol/L. At these, sensitivity was 92.0% and 90.7%, specificity 48.7% and 25.4% and the areas under the ROC 0.82 and 0.73 for FPG and PPPG, respectively. Nine (12%) women could be diagnosed as having GDM on the basis of the FPG being above the threshold.

CONCLUSIONS

FPG is superior to 2-h PPPG for screening high-risk women for GDM. Nine women were diagnosed as having GDM on the basis of having an FPG above 7 mmol/L. FPG could reduce the number of OGTT needed by 40.9%, compared to 20.6% by PPPG. FPG is a less cumbersome and cost-effective screening test.

Glucose Screening in Mexican-American Women

OBJECTIVE

We sought to describe the predictive value for gestational diabetes mellitus (GDM) using different glucose challenge test thresholds in Mexican-American women.

METHODS

A prospective population-based study of 6,857 gravid women, who were tested with a 50-g glucose challenge test at 24-28 weeks of gestation, was performed. A screening value of 130 mg/dL or greater was followed by a 3-hour, 100-g oral glucose tolerance test. Gestational diabetes mellitus was diagnosed by 2 or more abnormal values using the Carpenter and Coustan criteria. For purpose of analysis, GDM diagnosis was categorized with glucose challenge test values in 10-mg/dL increments. A comparison between Carpenter-Coustan and the National Diabetic Data Group criteria for GDM diagnosis was performed for each glucose challenge test threshold category. Sensitivity and specificity for GDM diagnosis were further calculated for different glucose challenge test thresholds (130, 135, and 140 mg/dL).

RESULTS

Overall, GDM was diagnosed in 469 of 6,857 (6.8%) women, and one abnormal oral glucose tolerance test value was tested in 351 of 6,857 women (5.1%). Normal glucose challenge test results (threshold less than 130 mg/dL) were obtained in 4,316 of 6,857 women. An elevated glucose challenge test value increases the risk of GDM, but even in high glucose challenge test thresholds (more than 180 mg/dL), the predictive value for GDM was only 50%. The sensitivity and specificity for GDM diagnosis using 3 different glucose challenge test thresholds were as follows: threshold 130 mg/dL or more: 97% and 63%; threshold 135 mg/dL or more: 91% and 73%; and threshold 140 mg/dL or more: 85% and 78%, respectively.

CONCLUSION

Data suggests that an elevated glucose challenge test level cannot be used as a single diagnostic tool for GDM even in high test thresholds. A threshold of 130 mg/dL may be recommended as a screening threshold for GDM in Mexican-American women.

LEVEL OF EVIDENCE

II-3

Comparison of two diagnostic tests for gestational diabetes in predicting macrosomia

OBJECTIVES

To validate a diagnostic test for gestational diabetes which predicts the risk of macrosomia.

METHODS

A prospective study was carried out among 354 women at risk for gestational diabetes to compare two glucose tests diagnosing pregnancies at risk of macrosomia. The "practical" test consisted in glucose measurement in the fasting state and two hours after an usual breakfast and the "reference" test was the test proposed in France (O'Sullivan test with or without a 100 g oral glucose tolerance test). Both tests were made between the 24(th) and 28(th) week of gestation. Women at high risk for macrosomia were treated. The first assessment criterion was macrosomia (babies large for gestational age). Because of the presence of women treated for gestational diabetes in our sample, the sensitivity and specificity of the tests in diagnosing pregnancies at risk of macrosomia were calculated using either the incidence of macrosomia observed in our population, or the incidence of macrosomia observed theoretically in the absence of treatment (22% in literature).

RESULTS

Macrosomia was diagnosed in 49 neonates (14%). The "practical" test was significantly more sensitive than the reference test (respectively 46.9% versus 16.3%, p=0.0001 in the first case, and 54.3% versus 20.1%, p=0.0001 in the second case). The "reference" test was significantly more specific than the "practical" test (respectively 80% versus 68.2%, p=0.0001 in the first case, and 80.6% versus 70%, p=0.0001 in the second case).

CONCLUSION

Our study shows that the simplified "practical" test is more sensitive than the "reference" test currently used in France in screening women at risk of macrosomia.

The utility of a single test to identify women at risk for gestational diabetes

A number of single tests have been proposed as both screening and definitive tests of glucose intolerance during pregnancy. Despite limitations imposed by a lack of uniformity in methodology and definitions of gestational diabetes mellitus, there appears to be an independent relationship between some single-test results and clinically meaningful outcomes. Further study is needed to identify those glucose values above which women and their babies who are at risk for glycemia-related adverse outcomes may be identified.

Evidence-based diabetes screening during pregnancy

The concept of gestational diabetes was described more than a half century ago and has been studied extensively for more than 30 years. Available data indicate that the prevalence is highly variable, probably reflecting underlying risk factors. In addition, gestational diabetes is not a specific disease, but rather an abnormal laboratory value. Criteria for diagnosis are variable, and there is little agreement about who should be screened, if screening should be selective or universal, or how screening should be performed. Moreover, the most commonly used criteria in the United States differ from the European and World Health Organization standard criteria. This article describes the background for diabetes testing, current evidence for testing and diagnosis in pregnant women, "risks" of diagnosis, and various screening procedures and protocols, using data-based evidence when available. Midwifery practice recommendations are also made, including examination of risk factors as clinical decisions are made about guidelines.

Jelly beans as an alternative to a fifty-gram glucose beverage for gestational diabetes screening

OBJECTIVE

This study tested the hypothesis that a standardized dose of jelly beans could be used as an alternative sugar source to the 50-g glucose beverage to screen for gestational diabetes mellitus.

STUDY DESIGN

One hundred sixty pregnant women at 24 to 28 weeks' gestation were recruited for a prospective study to compare 2 sugar sources for serum glucose response, side effects, preference, and ability to detect gestational diabetes mellitus. Patients were randomly assigned to consume 50-g glucose beverage or 28 jelly beans (50 g simple carbohydrate). Serum glucose values were determined 1 hour later. The test was later repeated with the other sugar source. Finally, a 100-g 3-hour oral glucose tolerance test was performed. Participants completed a questionnaire recording subjective outcome variables. American Diabetes Association criteria were used to interpret all test results.

RESULTS

Among 136 participants completing the study no significant differences were found between 1-hour serum glucose values (116.5 +/- 27 mg/dL with 50-g glucose beverage, 116.9 +/- 23.6 mg/dL with jelly beans; P =.84), frequency of discrepant results (P =.47), sensitivity, specificity, or predictive value. Jelly beans yielded fewer side effects (38% with 50-g glucose beverage, 20% with jelly beans; P <.001) and were preferred by 76% of participants (P <.001). Five cases (3.7% incidence) of gestational diabetes mellitus were diagnosed, 3 with 50-g glucose beverage alone, 1 with jelly beans alone, and 1 with both sugar sources.

CONCLUSIONS

Jelly beans may be used as an alternative to the 50-g glucose beverage as a sugar source for gestational diabetes mellitus screening. The 2 sources provoke similar serum glucose responses. Patients report fewer side effects after a jelly bean challenge than after a 50-g glucose beverage challenge.

Gestational diabetes survey

OBJECTIVE

Our purpose was to determine how residents in obstetrics and gynecology and fellows in maternal-fetal medicine are currently being trained to diagnose and manage gestational diabetes mellitus.

STUDY DESIGN

Questionnaires were mailed to 202 obstetrics and gynecology residency program directors and 78 maternal-fetal medicine fellowship directors.

RESULTS

Sixty-four (82%) of the maternal-fetal medicine directors versus 142 (70%) of the residency directors responded. Universal screening, use of a 50 gm glucose challenge with a 1-hour-postingestion sample, no requirements for fasting before the screening test, use of two abnormal values on the 3-hour glucose tolerance test to define gestational diabetes mellitus, and initiation of insulin for elevated fasting glucose levels in spite of diet therapy were each recommended by > 90% of the respondents.

CONCLUSION

Although the optimal management of gestational diabetes mellitus remains controversial, program directors are in general agreement with many aspects of the diagnosis and management.

Relationship of fetal macrosomia to a 75g glucose challenge test in nondiabetic pregnant women

We determined in nondiabetic women, the relationship of plasma glucose values obtained 2 hours after a 75 g oral glucose challenge test (GCT) at 16-20 weeks' gestation, with the incidence of macrosomia in term deliveries (37-41 weeks' gestation). From 1988-1990, in a systematic screening programme data collected prospectively from 1,331 women were analysed retrospectively. Women with gestational diabetes or impaired glucose tolerance (n = 53) were excluded. The rest (n = 1,278) had no evidence of glucose intolerance including 1,215 women with normal plasma glucose by GCT (< 7.8 mmol/L 2 hours after 75 g oral glucose load) and 63 women with abnormal GCT but not abnormal value at a glucose tolerance test. The GCT values were divided into 5 groups: Group A (< 4.5 mmol/L), B (4.5-5.5 mmol/L), C (5.6-6.6 mmol/L), D (6.7-7.7 mmol/L) and E (> 7.8 mmol/L). The variables studied were age, parity, gestational age at delivery and incidence of macrosomia. Using > 4 kg birth-weight as the definition of macrosomia, the incidence increased from 1.2% to 9.5% with increasing plasma glucose values in the GCT from Group A (> 4.5 mmol/L) to E (> 7.8 mmol/L). Similar trends of increasing incidences from 7.2% to 15.8% and 2.9% to 9.5% were noted when 90th and 95th birth-weight percentiles, respectively were used as definitions of macrosomia. The test of linear trend in this association was significant (p < 0.01). These results were not influenced by parity or gestational age at delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of repeat glucose tolerance tests in the diagnosis of gestational diabetes

The diagnosis of gestational diabetes requires that two of the four 100 gm, 3-hour oral glucose tolerance test values be elevated. Our report evaluates the usefulness of repeating the oral glucose tolerance test in patients who have only one abnormal value. One hundred six patients who had abnormal results of diabetes screening tests (glucose level greater than or equal to 130 mg/dl) and whose glucose tolerance test had one abnormal value underwent repeat glucose tolerance testing at an average of 4.6 weeks later. Thirty-six patients (34%) had two abnormal values on the repeat test and were classified as having gestational diabetes. Our results indicate that the finding of one abnormal value on a glucose tolerance test denotes a significant risk for the development of gestational diabetes.

Gestational diabetes mellitus: evidence for autoimmunity against the pancreatic beta cells

Diabetes mellitus is a frequent transient or rare permanent complication of pregnancy. The role of autoimmune phenomena in this gestational form of diabetes is incompletely understood. We have examined sera from 312 pregnant women who had abnormal glucose tolerance (based on a screening examination during the second trimester) for the presence of islet cell surface antibodies or insulin autoantibodies. Fifty-eight of these women were lost to follow-up. Of the remaining subjects, 144 (57.1%) had gestational diabetes diagnosed by formal glucose tolerance testing and the others (42.9%) were normal. Sixty percent of the women with gestational diabetes eventually required insulin to control their blood glucose during pregnancy. One serum from the non-diabetic women was positive for insulin antibodies (0.9%); 8 of the sera from the patients with gestational diabetes were positive (5.6%). Subsequent analysis revealed that all nine of the women whose sera were positive for insulin autoantibodies had been treated with insulin previously. Islet cell surface antibodies were strongly correlated with gestational diabetes. Forty-five of 144 gestational diabetic sera were positive (31.3%) whereas only 9 of 108 suspect control sera (8.3%) and 7 of 60 unknown sera (11.7%) were positive. These data suggest that a high percentage of pregnant women who screen positive for glucose intolerance have serological evidence of an autoimmune response against the pancreatic islets, in spite of the state of relative immune tolerance during pregnancy. These data suggest that autoimmune phenomena may play a role in gestational diabetes and that the presence of islet cell antibodies can predict insulin-requiring gestational diabetes.

Screening and diagnosis of gestational diabetes

This chapter discusses the evidence for the existence of an entity called 'gestational diabetes', suggesting that it can be understood in terms of risk to the pregnancy and/or risk to the mother. Various diagnostic criteria used in various parts of the world are described, and a rationale for using pregnancy-specific criteria is put forth. Universal screening approaches are also characterized. Barriers to the universal adoption of a single screening scheme and set of diagnostic criteria are outlined.

Reproducibility of the oral glucose tolerance test in pregnancy

This prospective investigation evaluated the reproducibility of the 100 gm oral glucose tolerance test. Sixty-four obstetric patients with greater than or equal to 135 mg/dl on the 50 gm oral glucose screening test were scheduled for the 100 gm test. All patients repeated the oral glucose tolerance test in 1 to 2 weeks. Both tests included a preparatory diet, and testing conditions were identical. There were no significant differences in the mean test values at each testing interval when the entire study population was considered. Patients were then divided into four groups according to the outcome of the two tests. Forty-eight of 64 (75%) had normal results at each testing period (group 1); 11 of 64 (17%) had initially normal results and abnormal results on retest (group 2); 3 of 64 (5%) had initially abnormal results and normal results on retest (group 3); 2 of 64 (3%) had abnormal results at both testing phases (group 4). There were no significant differences between oral glucose tolerance test results within groups 1 and 4. However, significant differences occurred within groups 2 and 3 between the two tests. Group 2 patients had a greater frequency of an abnormal 1-hour value on the test than group 1 patients (p = 0.001). Overall, the reproducibility of the oral glucose tolerance test was 78% (50 of 64). We recommend the oral glucose tolerance test be repeated when the 1-hour value is abnormal or when the fasting blood sugar, 1-hour, and 2-hour values are near the upper end of the normal range.