NEW YORK (Reuters Health) – Abnormal glucose tolerance can be detected by a carbon-13 labeled oral glucose tolerance test in which 13-CO2 excreted in the breath is measured with a standard breath analyzer, according to research conducted at the University of Texas Medical Branch in Galveston.

“This novel breath test method may assist in recognition of pre-diabetes or early-stage diabetes in at-risk persons without the need for invasive blood sampling, thus making it an attractive option for large-scale testing of at-risk populations, such as children,” Dr. Melinda Sheffield-Moore of the University of Texas Medical Branch in Galveston and co-investigators report in the March issue of Diabetes Care.

The research team collected blood and breath samples from 17 subjects at baseline and every 30 minutes for 10 hours after they consumed a drink containing 75 g glucose and 150 mg radiolabeled glucose. The investigators measured ratios of labeled-to-unlabeled CO2 in single breath samples using an infrared spectrophotometer.

Standard oral glucose tolerance test results indicated that 10 of the subjects had normal glucose tolerance (2-hour blood glucose < 7.8 mmol/L), and 7 had either pre-diabetes or early-stage diabetes (2-hour blood glucose 7.8-16 mmol/L). Mean fasting plasma glucose levels in the two groups were 5.1 and 6.8 mmol/L, respectively.

“Remarkably,” the authors write, “the breath analyzer was capable of detecting marked differences in glucose-derived breath CO2 kinetics between individuals (with normal and impaired glucose tolerance) within 60 minutes.”

The results showed that 13-CO2 abundance was significantly lower in the group with impaired glucose tolerance than in the nondiabetic subjects between 1 and 3 hours after the glucose load. Furthermore, the 2-hour 13-CO2 measurements significantly correlated with three measured indices of insulin resistance.

“The use of a point-of-care diagnostic breath 13-CO2 analyzer and storable breath collection bags is suitable for large-scale population testing in research as well as the clinical setting,” Dr. Sheffield-Moore’s and her associates note.

They anticipate future research to validate their findings and to establish diagnostic cutoff values.

Reference:
Diabetes Care 2009;32:430-435.