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Diagnostic ability of elevated 1-h glucose challenge test
L A Temming1, M G Tuuli1, M J Stout1
1Department of Obstetrics and Gynecology, Washington University in St Louis, St Louis, MO, USA.
Summary
A 1-hour glucose challenge test (GCT) threshold can identify many cases of gestational diabetes mellitus (GDM). However, omitting the 3-hour glucose tolerance test (GTT) risks overdiagnosing GDM in 20-33% of pregnant individuals.
Area of Science:
- Obstetrics and Gynecology
- Endocrinology
- Clinical Diagnostics
Background:
- Gestational diabetes mellitus (GDM) diagnosis typically involves a two-step process.
- The 1-hour glucose challenge test (GCT) is a screening tool, often followed by a 3-hour glucose tolerance test (GTT) for confirmation.
Purpose of the Study:
- To evaluate if a specific threshold on the 1-hour GCT can reliably replace the need for a 3-hour GTT.
- To determine the diagnostic accuracy of elevated 1-hour GCT values in identifying GDM.
Main Methods:
- Retrospective cohort study of patients undergoing both GCT and GTT.
- Analysis of GCT results (160-220 mg/dL) and subsequent GTT outcomes.
- Diagnosis of GDM using National Diabetes Data Group (NDDG) and Carpenter-Coustan (CC) criteria.
Main Results:
- Of 6218 patients, 753 underwent GTT after an elevated GCT.
- GDM diagnoses were 2.7% (NDDG) and 4.0% (CC).
- A 1-hour GCT ≥200 mg/dL had a positive predictive value of 68.6% (NDDG) and 80.0% (CC) for GDM.
Conclusions:
- While a 1-hour GCT ≥200 mg/dL shows high predictive value, omitting the 3-hour GTT could lead to overdiagnosis.
- Current GCT thresholds may not sufficiently differentiate between GDM and normal glucose tolerance, necessitating the GTT.
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