Dried blood spot screening can diagnose early neonatal diabetes
medwireNews: Neonatal diabetes could be detected as early as day 5 of life using glucose measurements from dried blood spots, researchers report.
“Earlier diagnosis by systematic screening could lead to prompt genetic diagnosis and targeted treatment, thereby avoiding the most severe sequelae of hyperglycaemia in neonates”, say Timothy McDonald (University of Exeter, UK) and co-investigators.
The study authors measured glucose levels using dried blood spots collected from babies at 5 days of age and applied an adjustment factor to account for variable degradation of the sample. A normal blood glucose range of 3.2–6.0 mmol/L was established using measurements from 687 newborns without diabetes.
They found that all 11 newborns with genetically confirmed neonatal diabetes had glucose levels above the normal range, ranging from 10.2 to more than 30 mmol/L.
By comparison, glucose levels measured using dried blood spots taken from paired control neonates on the same day ranged from 2.3 to 6.2 mmol/L. Median glucose levels were 18.7 mmol/L for babies with neonatal diabetes versus 4.6 mmol/L for those without, a significant difference.
These findings suggest that “[n]eonatal diabetes can be detected on day 5 of life, preceding conventional diagnosis in most cases”, write the study authors in Diabetologia. Indeed, the age of participants at diagnosis of neonatal diabetes ranged from 2 to 112 days.
The team explains that as part of the current UK newborn screening program for rare metabolic diseases, dried blood spots are taken from neonates and sent to laboratories by post, meaning that “a putative screening test would require the analyte to be stable at room temperature for at least 48 h”.
In stability experiments, blood spot glucose samples were stable under all conditions tested for 3 days. When stored at room temperature, the samples degraded to 84% of baseline at 7 days and 81% at 14 days, but samples stored at –4oC or –20oC did not degrade over 14 days.
“The 3 day stability of blood spot glucose makes it a feasible test that could practically be measured within the time restrictions of the current UK newborn screening programme”, say the researchers.
Although their results provide “preliminary evidence to support further consideration of newborn screening”, McDonald and colleagues note that the study was limited by the small sample size of infants with neonatal diabetes, and the fact that the tests were performed retrospectively, meaning that “a number of assumptions” on the linear degradation of blood spot samples were made.
And they conclude: “A large prospective assessment of the screening strategy will be required to confirm that blood spot glucose is a viable screening strategy for neonatal diabetes and this will need to be accompanied by a health economic analysis.”
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