Comparison of 2-Hour Oral Glucose Tolerance Test and Hemoglobin A1C in the Identification of Pre-Diabetes in Women with Infertility and Recurrent Pregnancy Loss.
Level 4 - case-series / case-control
Retrospective cross-sectional diagnostic accuracy study without clinical outcome follow-up
PubMed 30923441 · doi:10.1177/1179558119831280
What was done
A retrospective diagnostic study evaluated whether hemoglobin A1c (HbA1c, pre-diabetes defined as 5.7%–6.4%) predicts pre-diabetes compared with a 75 g, 2-hour oral glucose tolerance test (2h GTT, pre-diabetes defined as 140–199 mg/dL) as the reference standard. The study included 242 women presenting with infertility or recurrent pregnancy loss to a university-affiliated reproductive clinic between January 2012 and December 2016, of whom 188 had both tests performed.
What was found
Pre-diabetes prevalence was 10.6% (20/188; 95% CI, 6.6%–16.0%) by 2h GTT and 44.1% (83/188; 95% CI, 36.9%–51.6%) by HbA1c. Among 89 women testing positive on either test, 14 (15.7%) had abnormal results on both, 6 (6.7%) had an abnormal 2h GTT with normal HbA1c, and 69 (77.5%) had an abnormal HbA1c with normal 2h GTT. Against the 2h GTT standard, HbA1c had a negative predictive value of 94.3% (95% CI, 88.0%–97.9%) and a positive predictive value of 16.9% (95% CI, 9.5%–26.7%).
Why it matters
A normal HbA1c reliably excludes an abnormal 2h GTT in women with infertility or recurrent pregnancy loss, but the two modalities demonstrate poor diagnostic agreement, with HbA1c diagnosing pre-diabetes at more than four times the rate of 2h GTT.
Limits
The study is a single-center retrospective analysis with 54 of 242 patients missing one of the tests. It did not evaluate reproductive outcomes, clinical follow-up, or the long-term significance of an isolated elevated HbA1c.
Cited by
- supports Nearly half of women experiencing infertility or recurrent pregnancy loss have undiagnosed pre-diabetes.