Valerie Anderson1, Chang Ye1, Mathew Sermer2, Philip W Connelly3, Anthony J G Hanley4, Bernard Zinman5, Ravi Retnakaran5. 1. Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto ON. 2. Division of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto ON. 3. Division of Endocrinology, University of Toronto, Toronto ON; Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael's Hospital Toronto ON. 4. Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto ON; Division of Endocrinology, University of Toronto, Toronto ON; Department of Nutritional Sciences, University of Toronto, Toronto ON. 5. Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto ON; Division of Endocrinology, University of Toronto, Toronto ON; Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto ON.
Abstract
OBJECTIVE: A common approach to screening for gestational diabetes mellitus (GDM) is the testing of all pregnant women with a one-hour, 50 g glucose challenge test (GCT), followed by a diagnostic oral glucose tolerance test (OGTT) when the GCT is positive (≥ 7.8 mmol/L). As only a small subset of those with a positive GCT will have GDM, many more women undergo the OGTT than may be necessary. In this context, we hypothesized that measurement of fasting capillary glucose (FCG) could provide a strategy for reducing the number of unnecessary OGTTs. Thus, we sought to identify a threshold level of FCG below which GDM could be ruled out following a positive GCT, without need for the OGTT. METHODS: Following a positive GCT, 888 women underwent measurement of FCG prior to their OGTT. We evaluated the test characteristics of FCG for identifying the 209 women diagnosed with GDM on the OGTT. RESULTS: Fasting capillary glucose was positively associated with each glucose measurement on the OGTT (all P < 0.001) and inversely related to insulin sensitivity and pancreatic beta-cell function (both P < 0.001). As FCG increased, the prevalence of GDM progressively rose (P < 0.001). However, the area under the curve of the receiver-operating characteristic curve for FCG in predicting GDM was modest (0.67). Although using an FCG threshold of 4.8 mmol/L could reduce the number of OGTTs by 28.4%, this approach would miss 18.2% of cases of GDM. CONCLUSION: Fasting capillary glucose is associated with glycemia, insulin sensitivity, and pancreatic beta-cell function. However, a single FCG measurement is insufficient for reliably ruling out GDM after an abnormal GCT.
OBJECTIVE: A common approach to screening for gestational diabetes mellitus (GDM) is the testing of all pregnant women with a one-hour, 50 g glucose challenge test (GCT), followed by a diagnostic oral glucose tolerance test (OGTT) when the GCT is positive (≥ 7.8 mmol/L). As only a small subset of those with a positive GCT will have GDM, many more women undergo the OGTT than may be necessary. In this context, we hypothesized that measurement of fasting capillary glucose (FCG) could provide a strategy for reducing the number of unnecessary OGTTs. Thus, we sought to identify a threshold level of FCG below which GDM could be ruled out following a positive GCT, without need for the OGTT. METHODS: Following a positive GCT, 888 women underwent measurement of FCG prior to their OGTT. We evaluated the test characteristics of FCG for identifying the 209 women diagnosed with GDM on the OGTT. RESULTS: Fasting capillary glucose was positively associated with each glucose measurement on the OGTT (all P < 0.001) and inversely related to insulin sensitivity and pancreatic beta-cell function (both P < 0.001). As FCG increased, the prevalence of GDM progressively rose (P < 0.001). However, the area under the curve of the receiver-operating characteristic curve for FCG in predicting GDM was modest (0.67). Although using an FCG threshold of 4.8 mmol/L could reduce the number of OGTTs by 28.4%, this approach would miss 18.2% of cases of GDM. CONCLUSION: Fasting capillary glucose is associated with glycemia, insulin sensitivity, and pancreatic beta-cell function. However, a single FCG measurement is insufficient for reliably ruling out GDM after an abnormal GCT.