Enhanced glucose processing in gestational diabetes diagnosis: Effects on health equity and clinical outcomes.

Objectives: Gestational diabetes is diagnosed using an oral glucose tolerance test (OGTT), which has limited accuracy, reproducibility and practicality. We assessed the effect of enhanced pre-analytical glucose processing upon glucose concentrations, gestational diabetes diagnosis, health equity and pregnancy outcomes, and if HbA1c was a suitable alternative.

Methods: We recruited pregnant women with ≥1 risk factor to a prospective observational cohort study of pregnancy hyperglycaemia, endocrine causes, lipids, insulin and autoimmunity (OPHELIA), from nine UK centres. During a 75 g antenatal OGTT (National Institute of Health and Care Excellence criteria), standard glucose processing was compared to enhanced glucose processing (storage on ice, rapid centrifugation, aliquoting and freezing <2.5 h).

Results: We recruited 1308 participants of mean (SD) age 31.5 years (5.0) and BMI 33.0 kg/m (6.8) of 82.5% white ethnicity, representative of the UK population. Enhanced glucose processing resulted in glucose levels ~0.6 mmol/L higher than standard glucose processing, increasing gestational diabetes diagnosis from 9% to 22%. Women with gestational diabetes on enhanced but not standard glucose processing (n = 165) were younger (31.9 vs. 33.2 years, p = 0.035), with a higher BMI (36.5 vs. 33.9 kg/m; p = 0.003), different ethnic distribution (p = 0.025) and delivered more large-for-gestational age infants (37.0% vs. 22.3%; p = 0.006) compared to women with gestational diabetes on standard processing alone. HbA1c was not a suitable alternative predictor of gestational diabetes diagnosis (Area under receiver operator curve 0.74; 95% CI 0.68-0.79).

Conclusions: An OGTT with enhanced glucose processing would support more accurate, equitable diagnosis of gestational diabetes, but with increased diagnosis rates.