Evaluation of postpartum dysglycemia by serum glycosylated hemoglobin in patients with gestational diabetes mellitus: a national data analysis

To assess the postpartum sensitivity and accuracy of serum HbA1c levels, compared to the gold standard of 75-g Oral Glucose Tolerance Test (OGTT), for diagnosis of dysglycemia in patients with a history of gestational diabetes mellitus (GDM).

A nationwide retrospective analysis of individuals with a history of GDM and with records of both postpartum 2 h-OGTT and serum HbA1c measured anytime between delivery until 12 months post-delivery. Results were stratified into 3 different intervals: 0–3 months, 3–12 months, and > 12 months after delivery, according to the timing of both OGTT and HbA1c performance.

Between January 1st, 2015, until December 31st, 2021, a total of 55,119 individuals were screened, and 9,118 were diagnosed with GDM. Overall, 677 of the 9,118 individuals with GDM had laboratory results of both serum HbA1c levels and 2 h 75-gm-OGTT values after delivery. The overall Pearson correlation coefficient between HbA1c and 2 h-OGTT was 0.21 (P < 0.0001). However, when the OGTT results were stratified into 2 h-glucose values ≥ 200 mg/dL, a ROC curve yielded an Area Under the Curve (AUC) of 91.4% [95% CI: 83.9%-98.9%], with HbA1c levels of 5.7% yielding 80.0% sensitivity and 80.8% specificity (95% CI: 44.39–97.48%).

In patients with a recent diagnosis of GDM, serum HbA1c may be used as an auxiliary tool for postpartum diagnosis of dysglycemia.