Globally, gestational diabetes (GDM) is increasing at an alarming rate. This increase is linked to the rise in obesity rates among women of reproductive age. GDM poses a major global health problem due to the related micro- and macro-vascular complications of subsequent Type 2 diabetes and the impact on the future health of generations through the long-term impact of GDM on both mothers and their infants. Therefore, correctly identifying subjects as having GDM is of utmost importance. The oral glucose tolerance test (OGTT) has been the mainstay for diagnosing gestational diabetes for decades. However, this test is deeply flawed. In this review, we explore a history of the OGTT, its reproducibility and the many factors that can impact its results with an emphasis on pregnancy.

Background: Adopting the WHO protocol for glucose analysis is arguably impractical in the routine clinical setting. Deviations may develop due to a lack of understanding regarding the impact of glycolysis on the accuracy of results. Aim: We sought to assess the stability of glucose in two different blood collection tubes (BCT), BD Vacutainer® FX ‘Fl-Ox’ and Greiner Vacuette® FC-Mix ‘FC-Mix’ stored at room temperature (RT:18–22°C) and 4°C over 8.5 days. Method: Each participant provided venous whole blood collected into 51 BCTs; ‘Fl-Ox’ (n = 26) and ‘FC-Mix’ (n = 25). One Fl-Ox sample from each participant was handled according to the WHO recommended method. The remaining BCTs were stored at 4°C/RT prior to analyses at designated study timepoints. Glucose was measured using the hexokinase assay on the Cobas® 8000 platform. Results: Participants (n = 8, Male = 2) were aged 24–56 years. Plasma glucose measured in FI-Ox BCTs according to the WHO sample-handling method had a median concentration of 5.73 mmol/L (Range: 5.39–10.37 mmol/L). Glucose decreased by greater than minimal difference (>0.26 mmol/L) in blood collected into Fl-Ox and stored @4°C/RT within 24 h of phlebotomy. FC-Mix BCT maintained glucose <0.26 mmol/L @4°C over a period of 8.5 days and up to 4 days @RT when compared to the WHO recommended method. Conclusion: Glucose in FC-Mix BCT stored @4°C demonstrated the best agreement with results determined using the WHO specifications. When FC-Mix tubes were stored @RT, glucose was stable for 4 days. These findings suggest that the FC-Mix BCT effectively inhibits glycolysis and should be introduced into routine clinical practice.