Capillary Glucose Concentration during Oral Glucose Tolerance Test for the Diagnosis of Gestational Diabetes in Dakar (Senegal)

Objectives: Due to financial constraints, adherence to the gestational diabetes mellitus (GDM) screening guidelines in sub-Saharan Africa poses significant challenges. This study aims to evaluate the efficacy of more cost-effective glycaemic tests utilized in clinical practice, such as capillary blood glucose measurements. Methods: We conducted a prospective study in the Pikine National Hospital (Dakar, Senegal) from January 1, 2019, to June 31, 2023. Simultaneous measurements of venous and capillary blood glucose (VBG and CBG) were performed during a 75 g oral glucose tolerance test (OGTT). The International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria were employed for the diagnosis of GDM. Results: The study comprised 335 pregnant women, with a mean age of 30 years. The prevalence of GDM was 55% based on CBG measurements, compared to 30% for VBG. A significant association was observed between capillary and venous measurements. CBG tests overestimated blood glucose levels relative to VBG by +0.13 g/L (H0 and H1) and +0.06 g/L (H2). The bias was significant, with 95% of deviations falling outside acceptable margins at all stages of the OGTT. The sensitivity and specificity of CBG for diagnosing GDM were 78.2% and 54.7%, respectively. The negative predictive value was 85%, and the negative likelihood ratio (LR) was 0.39. CBG exhibited limited utility in diagnosing GDM (AUC = 0.66), with moderate contributions at H1 and H2 (AUC = 0.77 and 0.79). Conclusion: Given its favourable negative predictive value and low LR, CBG may serve as a useful initial screening tool, particularly when normal conditions VBG testing are not met.