OGTT curve shape could aid type 1 diabetes risk prediction
medwireNews: The shape of the curve obtained from an oral glucose tolerance test (OGTT) is associated with the incidence of type 1 diabetes among at-risk people, research shows.
In line with findings for type 2 diabetes risk, the researchers found that people who had a biphasic OGTT curve had a significantly lower cumulative incidence of diabetes during follow-up.
People with a biphasic response comprised 895 of the total 2627 study participants, who were all autoantibody-positive relatives of type 1 diabetes patients from the TrialNet Pathway to Prevention study. During follow-up lasting around 8 years, 9% of people with a biphasic response developed type 1 diabetes, compared with 21% of the monophasic group.
Participants with a biphasic curve were significantly younger than those with a monophasic response (11.5 vs 13 years), with 24% versus 34% being older than 18 years, and were less likely to have multiple autoantibodies (55 vs 68%), but the difference in diabetes incidence remained significant after accounting for these factors, as well as sex and BMI z score.
In addition to the reduced risk associated with a biphasic curve, Heba Ismail (University of Pittsburgh, Pennsylvania, USA) and co-researchers also found risk differences among patients with monophasic curves, based on the timing of the glucose peak.
The rates of diabetes were 13%, 23%, and 31% among people with glucose peaks at around 30, 60, and 90 minutes, respectively. After accounting for age, sex, BMI z score and number of autoantibodies, people with peaks at 60 and 90 minutes were a respective 1.57- and 1.87-fold more likely to develop diabetes than those with a peak at 30 minutes.
These observed differences “indicate that the monophasic glucose patterns should not be considered a uniform entity,” write the researchers in Diabetologia.
Ismail and team found that having a biphasic OGTT curve, and a lower overall glucose response, was associated with having a higher early C-peptide response, although they say that it “remains unclear […] why there was a second increase in the glucose concentrations in the biphasic subgroups.”
However, C-peptide responses were “generally inconsistent” across the subgroups with monophasic curves, leaving no obvious explanation for the differences in glucose peaks and diabetes risk. Most C-peptide measures were higher in the 30-minute peak group than the 90-minute peak group, but the reverse was true for 2-hour C-peptide, and most measures in the 60-minute group did not fall between those of the other two groups.
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