HbA1c and biomarkers of diabetes mellitus in Clinical Chemistry and Laboratory Medicine: ten years after

Since its discovery in the late 1960s, HbA_1c has proven to be a major biomarker of diabetes mellitus survey and diagnosis. Other biomarkers have also been described using classical laboratory methods or more innovative, non-invasive ones. All biomarkers of diabetes, including the historical glucose assay, have well-controlled strengths and limitations, determining their indications in clinical use. They all request high quality preanalytical and analytical methodologies, necessitating a strict evaluation of their performances by external quality control assessment trials. Specific requirements are needed for point-of-care testing technologies. This general overview, which describes how old and new tools of diabetes mellitus biological survey have evolved over the last decade, has been built through the prism of papers published in Clinical Chemistry and Laboratory Medicine during this period.

Interventions to support women with overweight or obesity or gestational diabetes mellitus to initiate and continue breastfeeding: Systematic review and meta-analysis

Exclusive breastfeeding is recommended for the first 6 months of life and benefits both mother and child. Women with overweight/obesity or gestational diabetes are at risk for poor breastfeeding outcomes. This review evaluates the efficacy of breastfeeding interventions in these at-risk populations. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Five databases were searched for interventions from inception to May 2020. Nineteen trials including 2,740 participants, 226 of which were dyads, were included. Intervention increased any breastfeeding at ≥6 months (OR 1.43, 95% CI [1.05-1.95]), and women in the intervention group were 90% more likely to exclusively breastfeed at 1-2 weeks (OR 1.9, 95% CI [1.17-3.09]) and more than twice as likely to exclusively breastfeed at 4-6 weeks (OR 2.23, 95% CI [1.27-3.90]) within the sensitivity analysis. These findings support breastfeeding interventions improving exclusive early postpartum breastfeeding and any breastfeeding from 6 months in women with gestational diabetes or obesity/overweight. Further randomized controlled trials with harmonized breastfeeding outcome reporting are needed to confirm efficacy.

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.

The diagnosis of gestational diabetes mellitus (GDM) using a 75 g oral glucose tolerance test: A prospective observational study

AIMS

Screening for Gestational Diabetes Mellitus (GDM) is controversial. This prospectivestudy compared different sets of diagnostic cut-off points for plasma glucose measurements following a 75 g Oral Glucose Tolerance Test (OGTT).

METHODS

Women who had maternal risk factors for GDM were recruited at their convenience attheir first prenatal visit and consented to a one-step OGTT at 26-28 weeks gestation.All women fulfilling the World Health Organization (WHO) 2013 diagnostic criteriareceived standard care for GDM.

RESULTS

Of the 202 women, 139 (69%) had one risk factor for GDM and 63 (31%) had > 1.Using the WHO criteria, 53% (n = 108) had GDM compared with 35% (n = 71) usingCanadian criteria and 18% (n=36) using National Institute for Health Care Excellencecriteria (NICE) criteria (both p<0.001). Of the 108 women, 50% (n = 54) requiredpharmacological treatment to control hyperglycaemia. If the Canadian criteria wereapplied, 11/54 (20.4%) women would not have received hypoglycaemics. If the NICEcriteria were applied, 36/54 (66.7%) women would not have received hypoglycaemics.Maternal insulin, HOMA-IR and C-peptide measured at the time of the OGTT showed evidence of increased insulin resistance in women who had GDM based on the WHOcriteria but who had a normal OGTT based on the Canadian or NICE criteria.

CONCLUSIONS

Under stringent research conditions, our study suggeststhat the Canadian and, in particular, the NICE criteria are not identifying women who may benefit fromimproved glycaemic control. These findings support the need for the planned review of the NICE guidelines on GDM in 2020.

Recommended pre-analytical plasma glucose sampling methodology may distort gestational diabetes mellitus prevalence: implications for diagnostic thresholds

AIM

Current International Association of the Diabetes and Pregnancy Study Groups/World Health Organization gestational diabetes mellitus (GDM) diagnostic thresholds are based on a landmark study in which the pre-analytical plasma glucose sampling methodology is unclear. Worldwide, plasma glucose pre-analytical sampling methodology practices are divergent. We considered the effects of pre-analytical plasma glucose sampling methodology on GDM prevalence and gestational outcomes.

METHODS

This is a retrospective observational cohort study of 1178 pregnant women undergoing an oral glucose tolerance test (OGTT). Of the 1178 pregnant women, a subset of 892 non-GDM women with singleton births undergoing OGTT between 24 and 28 weeks' gestation were investigated for large for gestation age (LGA) outcomes. OGTT were determined using traditional methods (sodium fluoride tubes batched at roomed temperature). We modelled the potential effects of using a recommended pre-analytical plasma glucose methodology (lyophilized citrate tubes) on GDM prevalence.

RESULTS

The GDM prevalence in our cohort was 13.5%. The incidence of LGA showed a linear association with maternal plasma glucose that was similar to the association observed in the Hyperglycemia and Adverse Pregnancy Outcome study. Frequency of LGA exceeded 10% at HAPO glucose category 4 (fasting, 4.8 to 4.9 mmol/l; 1-h, 8.7 to 9.5 mmol/l) for fasting and 1-h plasma glucose. The use of a recommended pre-analytical method is projected to increase the prevalence of GDM to 39.2%.

CONCLUSION

We challenge the consensus that recommended pre-analytical plasma glucose methodologies are optimal for the accurate diagnosis of GDM. Recommended pre-analytical plasma glucose methods may profoundly over-diagnose GDM. Centres using recommended pre-analytical plasma glucose methodologies may need to reappraise their diagnostic thresholds.

A comparison between point-of-care testing and venous glucose determination for the diagnosis of diabetes mellitus 6-12 weeks after gestational diabetes

AIM

To evaluate point-of-care-testing (POCT) for the diagnosis of Type 2 diabetes mellitus 6-12 weeks post-partum in women with gestational diabetes (GDM).

METHODS

Post-partum glucose assessment (75-mg oral glucose tolerance test, OGTT) was performed prospectively in 122 women with GDM (1 November 2015 to 1 November 2017) at Tygerberg Hospital, Cape Town, South Africa. Individuals with known pre-existing diabetes were excluded. The accuracy and clinical utility of POCT (capillary finger-prick) were compared with laboratory plasma glucose (hexokinase and glucokinase methods). The OGTT consisted of two time points (fasting and 2 h) during which concurrent glucose samples (POCT and laboratory) were obtained. Bland-Altman plots and paired analysis were used to assess the analytical accuracy of POCT, whereas its diagnostic performance was determined using positive and negative predictive values to calculate specificity and sensitivity.

RESULTS

Spearman's ranked correlation analysis indicated a strong association between POCT and laboratory glucose values at both OGTT time points (fasting, r = 0.95, P < 0.0001; 2 h, r = 0.88, P < 0.0001). Thirty-six women were diagnosed with Type 2 diabetes based on gold standard laboratory glucose levels (fasting > 7 mmol/l; 2 h > 11.1 mmol/l). POCT correctly identified Type 2 diabetes in 78% of women (28 of 36) with a positive predictive value of 89.3% and a negative predictive value of 96.7% at the fasting time point. The sensitivity and specificity of POCT to diagnose Type 2 diabetes were 89% (fasting), 85.7% (2 h) and 96.7% (fasting), 98.5% (2 h) respectively. POCT proved less sensitive to diagnose pre-diabetes (69%) but displayed satisfactory specificity (92%) at both time points assessed.

CONCLUSION

POCT accurately identifies women with Type 2 diabetes 6-12 weeks after GDM.