BLOOD SCIENCES
What gestational diabetes can teach us about the future of diagnostics
The diabetes test is only as good as the pathway around it; with improved sample handling resulting in a significant rise in positive results. James Jackson asks what this can teach laboratory professionals about the future of diagnostics.
Gestational diabetes mellitus (GDM) is now the most common medical complication of pregnancy in the UK, yet recent research suggests that the way blood samples are handled may materially influence who receives a diagnosis. For laboratory professionals, the underlying issue will be familiar. Glycolysis begins as soon as whole blood is collected, and delays between venepuncture and sample processing can result in measurable glucose consumption before analysis. What is particularly significant about the latest evidence is the extent to which this familiar pre-analytical issue can translate directly into differences in clinical diagnosis. The NIHR-funded OPHELIA study,
conducted across nine UK centres and involving 1,308 pregnant women undergoing a 75 g oral glucose tolerance test (OGTT), provides compelling evidence. Researchers compared ‘standard’ sample processing procedures with ‘enhanced’ sample processing involving storage on ice, rapid centrifugation, aliquoting and freezing within two and a half hours. Enhanced processing produced
glucose results approximately 0.6 mmol/L higher than standard processing. Given that GDM is diagnosed against defined glucose thresholds, this difference had a substantial effect: the proportion of women diagnosed with GDM more than doubled, from 9% with standard processing to 22% with enhanced processing. This difference in diagnosis has been seen around the world, with
60% or more missed cases of GDM being reported with standard processing. It should be noted that enhanced
processing methods were used in all the work conducted to establish diagnostic thresholds found in clinical guidelines. For pathology services, this is important because it demonstrates that pre- analytical variation is not simply an issue of analytical performance. In a threshold- based diagnostic test, it can determine
whether a woman is diagnosed at all – and therefore whether she enters the pathway for treatment and monitoring.
When pre-analytical variation affects diagnosis
The OPHELIA findings build on a well- established understanding of glucose stability. Fluoride-containing tubes inhibit glycolysis, but inhibition is not instantaneous, meaning that collection-
A recent study compared OGTT results with standard procedure and ‘enhanced’ sample processing, which included rapid centrifugation among other measures to speed up the process.
October 2026
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