Is there a place for a single value oral glucose tolerance test for the diagnosis of gestational diabetes mellitus?

The oral glucose tolerance test (OGTT) is the recommended diagnostic test for gestational diabetes mellitus (GDM). There is no consensus regarding the diagnostic criteria and OGTTs described by the World Health Organization (WHO) [1] and the American Diabetes Association [2] are the tests most frequently used. In 1999, the WHO changed the threshold values for the 75g OGTT to a fasting venous plasma glucose (FPG) value of ≥ 7.0 mmol/L and/or a 2-h value of ≥ 7.8 mmol/L [1]. One reason for this amendment was a discrepancy in the sensitivity of the previous threshold values [3]. The WHO criteria are based on studies done on non-pregnant populations, which show an increase in long term complications above these values [3]. South Asians are a high risk group for developing GDM and it is recommended that they be screened routinely [2]. In our unit, we screen only those with a further risk factor, such as obesity or a positive family history. We reviewed 2 500 consecutive OGTTs performed in our Reproductive Biology Laboratory on pregnant women from January 2002 to July 2003. An automated glucose oxidase colorimetric test kit was used to assay venous plasma glucose levels. Five hundred and twenty two (20.9%) had GDM by the current WHO criteria. The abnormalities in the GTTs are given in Table 1. The data show that if the OGTT was performed with only the 2-h value, 99.6% of the women with GDM would have been diagnosed with only a minimal loss of sensitivity.