Dextrose rebound hypoglycaemia — confounder for insulin/C-peptide reading
The prosecution’s claim: Babies F and L showed insulin/C-peptide patterns the prosecution treated as proof of exogenous insulin.
Prosecution claim
Babies F and L showed insulin/C-peptide patterns the prosecution treated as proof of exogenous insulin.
Counter-evidence
When dextrose treatment for neonatal hypoglycaemia is administered and then weaned, rebound hypoglycaemia is a recognised phenomenon driven by transient hyperinsulinism in response to the dextrose load. The Joint Expert Witness Insulin Report on Babies F and L sets out that a C-peptide reading taken from a dextrose-treated infant does not reflect baseline pancreatic function and cannot be used as a forensic marker without the paired pre-treatment sampling that was not performed. The Shoo Lee Panel's own conclusion is simpler and more fundamental: the insulin/C-peptide ratios in Children F and L were within the range normal for preterm infants and do not prove exogenous insulin. The hypoglycaemia itself, on the Panel's findings, is explained by prematurity, intrauterine growth restriction, sepsis and a tissued long line in Child F's case — and by inadequate management in both.
Key point: C-peptide is suppressed by dextrose treatment. The C-peptide reading taken after dextrose was given does not reflect the baby's baseline. Without pre-treatment sampling, the insulin/C-peptide pattern cannot bear the forensic weight it was given at trial.
What the jury heard
The insulin/C-peptide pattern was presented as diagnostic of exogenous insulin. The dextrose-treatment confounder for C-peptide was not foregrounded.
What the Panel says
The Panel's finding is that the insulin/C-peptide ratios in Children F and L were within the range normal for preterm infants and do not prove exogenous insulin; the hypoglycaemia is attributed to prematurity, growth restriction, sepsis, a tissued long line (Child F) and inadequate management. The Joint Expert Witness Insulin Report separately identifies dextrose-treatment effects on C-peptide as one of several confounders that place the insulin counts below the criminal-evidential threshold.
What independent experts add
- Adel Ismail's clinical-biochemistry commentary covers dextrose-rebound and other physiological confounders for the Cobas immunoassay.
- The dextrose-treatment confounder applies to both Babies F and L.
- The Panel's own answer to the insulin counts does not depend on the confounders at all: it found the insulin/C-peptide ratios to be within preterm norms.