Fasting Plasma Glucose at 24–28 Weeks to Screen for Gestational Diabetes Mellitus: New evidence from China

OBJECTIVE

To evaluate the usefulness of a fasting plasma glucose (FPG) at 24–28 weeks’ gestation to screen for gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

The medical records and results of a 75-g 2-h oral glucose tolerance test (OGTT) of 24,854 pregnant women without known pre-GDM attending prenatal clinics in 15 hospitals in China were examined.

RESULTS

FPG cutoff value of 5.1 mmol/L identified 3,149 (12.1%) pregnant women with GDM. FPG cutoff value of 4.4 mmol/L ruled out GDM in 15,369 (38.2%) women. With use of this cutoff point, 12.2% of patients with mild GDM will be missed. The positive predictive value is 0.322, and the negative predictive value is 0.928.

CONCLUSIONS

FPG at 24–28 weeks’ gestation could be used as a screening test to identify GDM patients in low-resource regions. Women with an FPG between ≥4.4 and ≤5.0 mmol/L would require a 75-g OGTT to diagnose GDM. This would help to avoid approximately one-half (50.3%) of the formal 75-g OGTTs in China.In 2011, the Ministry of Health (MOH) in China published the diagnostic criteria for gestational diabetes mellitus (GDM) based on a 75-g oral glucose tolerance test (OGTT) carried out between 24 and 28 weeks’ gestation (1). As a formal glucose tolerance test may be difficult to implement in low-resource rural areas in China, the MOH sought to assess whether a fasting plasma glucose (FPG) could be used as a screening tool to reduce the number of OGTTs required. The following cut points were suggested: if FPG ≥5.1 mmol/L, GDM can be diagnosed immediately; if FPG <4.4 mmol/L, GDM can be considered unlikely. Thus, the 75-g OGTT only needs to be performed for women with FPG values ≥4.4 mmol/L and <5.1 mmol/L. As there was no scientific evidence from China to support this approach, we conducted this study to test the hypothesis.