Diagnostic Performance of HbA1c Compared With OGTT for Detecting Gestational Diabetes and Associated Maternal Risk Factors in Ghana

Background The oral glucose tolerance test (OGTT), the reference standard for diagnosing gestational diabetes mellitus (GDM), is often challenging to implement in routine antenatal care. Glycated hemoglobin (HbA1c) is a simpler alternative, but evidence of its diagnostic performance during pregnancy is limited in sub-Saharan Africa. This study evaluated GDM prevalence, agreement between HbA1c and OGTT, and maternal factors associated with OGTT-diagnosed GDM in Ghana. Methods A cross-sectional study was conducted among 138 pregnant women attending antenatal care in Ghana. Participants underwent a 75-g OGTT and HbA1c testing between 24 and 28 weeks of gestation. Diagnostic performance of HbA1c relative to OGTT was assessed using sensitivity, specificity, predictive values, Cohen’s kappa statistic, and receiver operating characteristic (ROC) curve analysis. Multivariable logistic regression was used to identify maternal factors associated with GDM. Results The prevalence of GDM based on OGTT was 47.8% in this clinic-based sample. HbA1c ≥ 5.7% identified fewer cases (16.7%) and demonstrated low sensitivity (42.4%) but high specificity (100.0%) for detecting OGTT-defined GDM. Agreement between HbA1c and OGTT was moderate (κ = 0.44). ROC analysis showed discrimination (AUC = 0.862); however, the clinically applied threshold demonstrated limited sensitivity. Higher maternal body mass index and family history of diabetes were associated with increased odds of GDM. Conclusion The prevalence of OGTT-diagnosed GDM was high in this population. Although HbA1c demonstrated high specificity, its low sensitivity indicates that it cannot replace OGTT as a standalone screening test. These findings support the continued use of OGTT for GDM diagnosis, particularly in higher-risk populations.