A case of a 3 week old 3 week premature hypoglycemic white female in
the US yielded high insulin assays in conjunction with a very low
c-peptide results which gave rise to concerns about exogenous insulin
administration. The father is diabetic.
However, later media investigation yielded information that the blood
samples for insulin assay had been left on a window ledge in open
sunlight for significant periods, prompting an investigation by experts
retained by a film production company into the effect of holding blood
samples from their own lab. staff at elevated temperatures for differing
periods of time before spinning down.
Bloods left at temperatures of 98 deg F or 120 F resulted in high
insulin assays similar to some of the results in the child's case - one
of them in excess of 500,000 micro units/ml - compared with assays in
single or double figures from bloods left at 85 deg F or less for the
same periods of time.
There was some uncertainty over the storage of the spun down samples -
whether they were frozen in dry ice or not - so tests were redone with
all samples being frozen appropriately, and this time assays were
'normal'.
None of the experimental work, sadly, included assays of c-peptide in
the lab staff blood.
There is unsurprisingly some interest in the US as to what really was
going on in the original case - were the high insulin assaays
artefactual - might the very low c-peptide result - (0.05ng/ml) - also
be artefactual - is there a plausible explanation for these huge
variations in insulin assay other than the received wisdom that high
insulin - low c-peptide automatically means exogenous insulin?
Do any list members anywhere in the world have observations - is insulin
assay really so critically dependent on the correct storage of samples?
Can diagnosticians be certain standard operating procedures have been
followed when faced with such extraordinary results?
Brian Morgan
Freelance Journalist
|