Comparison the Carpenter and Coustan thresholds with the new thresholds obtained from Thai pregnant women for the diagnosis of gestational diabetes

AIMS

To determine the threshold of plasma glucose levels calculated from the mean+2SDs for diagnosing gestational diabetes mellitus (GDM) in Thai women.

METHODS

Thai pregnant women without pre-existing diabetes were invited into the study. A 100-g oral glucose tolerance test (OGTT) was performed in all participants during their second or third trimesters, regardless of the results of 50-g glucose challenge test.

RESULTS

Seven hundred and ninety seven women with singleton pregnancy participated in the study. The distribution of 1-, 2-, and 3-h plasma glucose levels of the 100-g OGTT was Gaussian. The rounded cut-off point values calculated from the mean+2SDs were 90, 195, 170, and 155 mg/dl, respectively for fasting, 1-, 2-, and 3-h plasma glucose. With the Carpenter and Coustan thresholds, 52 women (6.5%, 95%CI 4.9-8.5%) were diagnosed as GDM. Of these, when tested with the new thresholds, 30 had normal glucose tolerance and 22 were diagnosed as GDM.

CONCLUSION

By using mean+2SDs of plasma glucose levels of the 100-g OGTT as the threshold for diagnosing GDM, the thresholds at 1, 2, and 3h obtained from Thai women were 15 mg/dl higher than those of the Carpenter and Coustan thresholds.

Differences in postload plasma glucose levels between 100-g and 75-g oral glucose tolerance tests in normal pregnant women: a potential role of early insulin secretion

OBJECTIVE

To demonstrate a role of early insulin secretion on plasma glucose levels after different amounts of oral glucose loads in pregnant women.

MATERIAL AND METHOD

Forty-one pregnant women with normal glucose tolerance according to the Carpenter and Coustan' s criteria and 25 non-pregnant women (control group) with normal glucose tolerance according to the World Health Organization criteria were enrolled. Each subject was randomly scheduled to perform both the 100-g and 75-g OGTT within a 1-week interval. Venous blood was drawn at fasting, 30-, 60-, 120-, and 180-minute intervals during both tests for determination of plasma glucose and serum insulin levels.

RESULTS

The mean (+/- SE) ages of the pregnant and control groups were 33.3 +/- 0.9 and 31.8 +/- 1.4 years, respectively. The mean gestational age at the time of performing OGTT of the pregnant group was 28.7 +/- 0.6 weeks. In the non-pregnant group, the plasma glucose concentrations were not different between 75-g and 100-g OGTT whereas the serum insulin levels at the 30 and 180 minutes of the 100-g OGTT were significantly higher than those of the 75-g OGT. In the pregnant group, both plasma glucose and serum insulin concentrations at the 120 and 180 minutes of the 100-g OGTT were significantly higher than those of the 75-g OGT.

CONCLUSION

The limited ability of early insulin secretion to increase when glucose load increased in the pregnant women could explain the high plasma glucose levels at 2 and 3 hours of 100-g OGTT compared to those of 75-g OGTT.

A comparison between a 75-g and 100-g oral glucose tolerance test in pregnant women

OBJECTIVES

To test the validity of a 75-g, 2-h oral glucose tolerance test (OGTT) for diagnosing gestational diabetes mellitus (GDM) using the criteria and reference values suggested by the American Diabetes Association for the 100-g, 3-h OGTT.

METHODS

The results of a 75-g, 2-h OGTT were compared with those of a 100-g, 3-h OGTT in 42 pregnant women. The women's mean+/-S.D. age and gestational age were 33.6+/-5.4 years and 28.2+/-4.2 weeks, respectively. Each subject was randomly scheduled within 1 week for both the 75-g and 100-g OGTTs.

RESULTS

The mean plasma glucose concentrations at 1, 2, and 3 h during the 100-g OGTT were significantly higher than those during the 75-g OGTT. Using the Carpenter and Coustan criteria, the prevalence of GDM was 21.4% when using the 100-g, 3-h OGTT, whereas it was found to be at only 7.1% when using the 75-g, 2-h OGTT.

CONCLUSIONS

Plasma glucose responses during the 75-g OGTT were found to be lower than those during the 100-g OGTT. When using the same diagnostic criteria, the prevalence of GDM was also found lower using the 75-g glucose load. It would therefore not be appropriate to use the 75-g OGTT for diagnosing GDM using the criteria and reference values of the 100-g OGTT. To give a comparable prevalence of GDM, the threshold of abnormal plasma glucose levels of the 75-g OGTT would need to be lower than that of the 100-g OGTT.