Gestational diabetes

FBG strategy will avoid need for OGTT in pregnancy during pandemic

Gestational diabetes mellitus (GDM) should be diagnosed on the basis of fasting blood glucose (FBG) levels during the pandemic so that women are not required to spend hours in a testing facility undergoing oral glucose tolerance tests (OGTT), endocrinologists in Queensland say.

Around 80% of pregnancy OGTT tests could be avoided and social distancing maintained if a two-step FBG strategy is used instead during the COVID-19 pandemic, according to clinicians from the Royal Brisbane and Women’s Hospital.

Dr Michael D’Emden and colleagues in the Department of Endocrinology  have shown that a GDM screening strategy based on FBG < 4.7mmol/l would have a low rate of abnormal glucose tolerance and minimal adverse pregnancy-associated complications.

They analysed the POGTTs of 26,242 pregnant women in Queensland performed between January and June 2015 and found there were 3,946 (15%) patients having GDM. Of these, 2,262 (8.6%) had FBG ≥ 5.1mmol/l.

In a study published in PLOS One the receiver operator characteristics (ROC) assessment identified FBG levels >4.6mmol/l as having the best specificity (77%) and sensitivity (54%) for elevated one- and/or two-hour blood glucose levels (BGLs).

It found that 73.7% of women had FBG < 4.7mmol/l with a prevalence of GDM of 4.0%, less than one third the overall rate.

Only 4,638 (17.7%) women had indeterminate FBGs from 4.7–5.0mmol/l and would need to consider having a POGTT or undertake alternative strategies to assess glucose tolerance.

“This analysis suggests that a 2-step diagnostic pathway based on an initial FBG can be used to identify women having either “normal” glucose tolerance associated with a low risk in pregnancy-associated adverse outcomes, or women with GDM,” the researchers concluded.

“Importantly, adopting this 2-step approach still enables the effective identification of cases of GDM at increased risk of adverse pregnancy outcomes including those at highest risk having elevated fasting and post-load BGLs”

The study authors said FBG was a simple, inexpensive, reliable and readily understood measurement of glucose, better tolerated than the POGTT,  “that can have a role in the assessment of glucose intolerance in pregnancy in the current COVID-19 environment, in health care environments with limited resources and potentially in other clinical circumstances eg patients post bariatric surgery.”

“These data when considered together with the outcome data from a subgroup of HAPO suggests that this two step-diagnostic approach could be considered as a more efficient and cost-effective strategy for the diagnosis of GDM.

“It would significantly reduce the need for a POGGT and avoid labelling 25% of women with a diagnosis of GDM whose pregnancies are not associated with increased rates of adverse outcomes, avoiding providing un-necessary additional resources for education, blood glucose monitoring or therapeutic intervention.”

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