Oral glucose tolerance test predicts diabetes risk in relatives

Glycemic response to an oral glucose tolerance test may predict the development of diabetes in close relatives of patients with type 2 diabetes, researchers in Iran reported.

“Having one first-degree relative who is suffering from diabetes increases the risk of becoming diabetic to 40%,” Await Feizi, PhD, associate professor of biostatistics at Isfahan University of Medical Sciences, and colleagues wrote. “Identifying the ‘at risk’ population for prediabetes and [diabetes], such as the offspring of patients with type 2 diabetes, is important for medical and research purposes, so that appropriate prevention strategies could be employed.”

The researchers performed a population-based cohort study of 766 first-degree relatives of patients with type 2 diabetes. All participants completed a 2-hour oral glucose tolerance test and were followed for up to 7 years. Feizi and colleagues used American Diabetes Association criteria to classify participants as having normal glucose tolerance, impaired fasting glucose, impaired glucose tolerance, or diabetes. The researchers used receiver-operator characteristic analysis and area under the curve at different timepoints to estimate risk for diabetes or prediabetes.

Three percent (n = 23) of participants developed type 2 diabetes, the researchers reported, while 29.3% (n = 118) had impaired fasting glucose, 11.5% (n = 81) had impaired glucose tolerance and 71% (n = 544) maintained normal glucose tolerance.

In all high-risk groups in the study, area under the curve and mean difference of glucose showed significant differences in both timepoints and intervals compared with participants who had normal glucose tolerance, Feizi and colleagues wrote. The cutoff value to predict prediabetes and diabetes was glucose level above 7.2 mmol/L at 30 minutes and above 7.8 mmol/L at 60 minutes.

The 60-minute timepoint was the most predictive for diabetes “and improved the performance of a prediction model containing multiple important clinical risk factors,” the researchers wrote.

Feizi and colleagues wrote that the findings could be useful in identifying candidates for kidney donation among first-degree relatives of patients with diabetes; the increased risk for type 2 diabetes in those with elevated plasma glucose levels would make them unsuitable donors.

“More longitudinal studies should be conducted to investigate whether glucose response phenotypes could predict high-risk groups in [first-degree relatives] of patients with diabetes,” the researchers wrote. – by Andy Polhamus

Disclosures: The authors report no relevant financial disclosures.