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HbA1c Blood Test Shows Potential to Detect Risk of Gestational Diabetes

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NEW YORK (GenomeWeb) – A clinical chemistry assay that is frequently used to detect type II diabetes may someday be useful to detect risk of developing gestational diabetes as well, new research from the National Institutes of Health and other institutions suggests.

In a study published Scientific Reports earlier this month, researchers from the Eunice Kennedy Shriver National Institute of Child Health and Human Development and their colleagues showed that pregnant women who went on to develop gestational diabetes mellitus (GDM) later in pregnancy had significantly elevated HbA1c blood levels  as early as 10 weeks of gestation.

Being able to spot risk for GDM in the first trimester may someday enable early interventions, preventing serious health impacts for mother and baby. "Women with gestational diabetes have a high risk of developing pre-eclampsia later in pregnancy, which can be particularly dangerous, and also of undergoing a Cesarean delivery," explained Stefanie Hinkle, corresponding author on the study and a staff scientist at NICHD.

Babies are also endangered when a mom becomes glucose intolerant, Hinkle said. They have an increased risk of a higher birth weight than normal, or macrosomia, and of having neonatal hypoglycemia, shoulder dystocia, or other birth traumas. In the long term, they are also more likely to develop type II diabetes themselves, as well as cardiovascular disease and obesity.

The US Preventative Services Task Force guidelines recommend that all asymptomatic women be screened for GDM after the 24th week of pregnancy. If a woman screens positive on a glucose challenge test, that is then followed by a diagnostic test called the oral glucose tolerance test.

However, these tests are typically performed between weeks 24 and 28 of pregnancy. Women can be prescribed lifestyle interventions at this point – such as dietary changes and increased exercise – but, considering a pregnancy is around 40 weeks long, "it leaves you about 12 weeks for it to have any effect," Hinkle said.

The HbA1c assay measures glucose bound to hemoglobin. Since blood cells are replaced by the body regularly, the test essentially provides an average measure of a person's blood glucose level over the prior three months. This test is not typically used in pregnancy, but the NICHD study sought to determine whether it might be in the future.

The study was part of a larger project called The NICHD Fetal Growth Study, an observational epidemiologic study that recruited 2,334 low-risk pregnant women from 12 US clinical sites between 2009 and 2013 in order to identify race-specific fetal growth standards across pregnancy. That cohort included non-obese women as well as healthy obese women, screening out smokers, women taking certain medications, and those with other known risk factors for pregnancy complications. It yielded a new set of growth curves of normal baby weights through pregnancy, which vary by race and ethnicity, allowing doctors to more accurately discover babies growing abnormally and preventing overtreatment of women and babies whose development is normal given their racial background.

Using blood samples collected during the Fetal Growth Study, Hinkle and her colleagues examined HbA1c levels in 107 women who had gone on to develop GDM later in pregnancy and compared them to 214 matched controls using an HPLC assay from Tosoh Bioscience. They found that women who developed GDM had significantly elevated HbA1c from the earliest time point measured that lasted throughout their pregnancies.

Specifically, the median level was 5.1, with a 22 percent increased risk of developing GDM for each 0.1 increase in HbA1c levels. The researchers did not observe any non-linear associations.

Hinkle said her team in general studies the pathogenesis of GDM, and its ultimate goal is to understand how we could use a lot of different biomarkers together in one  prediction model. Regarding the results of the HbA1c study, she noted it was a small, observational study and that HbA1c cannot be used to diagnose GDM at this point. Her group has no plans to follow up at the moment, but Hinkle noted that the study "could set the stage for a randomized trial" that could test whether putting at-risk women on lifestyle interventions early could optimize their pregnancy outcomes later on.

Meanwhile, demand for new HbA1c assays to diagnose diabetes is reportedly increasing, and several firms have gotten US Food and Drug Administration clearances for HbA1c assays recently. These include the Tina-quant HbA1c Gen. 3 assay from Roche on its new Cobas c 513 analyzer; Siemens Healthineers' Advia Chemistry Enzymatic Hemoglobin A1c assay; the Abbott Afinion HbA1c Dx on its Afinion AS100 Analyzer; and the Sekure HbA1c assay from Sekisui Diagnostics.