Babies F and L were both found to have traces of medical insulin that would not have been produced naturally.
Not this again.
The babies were never tested for exogenous insulin. Nor was the TPN bag sent off for forensic testing. The claim that insulin was used is no more than that and is merely an inference made from the difference between insulin and c peptide levels in blood samples. (Insulin and c peptides are produced in equimolar amounts in the body). The test for insulin measures antibodies to insulin which are known to be easily contaminated by cross-reactants.
The kinetics of insulin and c peptides in preterm neonates are relatively unstudied, but one study highlights the following:
~ Preterm infant glucose-insulin metabolism differs significantly from adults.
~ Hyperglycemia in preterm neonates is common and associated with higher mortality
~ Insulin and c peptide levels are influenced by the organs that clear them - the kidneys clear c peptide and the liver and other tissues clear insulin.
~ C peptide is produced in equimolar quantities with insulin, and is principally cleared by the kidneys. Insulin is cleared by liver and peripheral tissues in a highly variable way, as well as the kidneys.
The physiology of neonates is immature and the variation in blood volume, liver metabolism and renal function affects the reliability of insulin and c peptides readings, so does cross reactivity with other proteins. This will produce very variable results requiring multiple samples to get a reliable reading, and very different readings to adults. Quite apart from the issue of incorrect storage and handling (which was denied but can’t be proven) and differing methods used by different labs producing variable results.
One of test result of 4657 pmol/L was so high as to kill an adults 4 times over. (A study of 12 suicides by insulin found the peripheral blood insulin found a maximum concentration of 930 pmol/L.)
The inventor of the test, Professor Vincent Marks, himself an expert witness at trials involving insulin, said the test should never be used in isolation due to the danger of false positives. He estimated the amount to kill an adult is around 1000 pmol/L.