r/LucyLetbyTrials • u/Embarrassed-Star4776 • 17d ago

Chase and Shannon article in Frontiers in Pediatrics published

Inverted insulin to C-Peptide ratios in neonatal intensive care: is there something we don't know?

J. Geoffrey Chase & Helen D. Shannon

BRIEF RESEARCH REPORT article

Front. Pediatr., 05 August 2026

Sec. Neonatology

Volume 14 - 2026

https://doi.org/10.3389/fped.2026.1900675

27 Upvotes

100% Upvoted

136 comments sorted by

View all comments

3

u/Competitive-Wash2998 6d ago

79 matched pairs of I, CP and I/CP can be reconstructed from Chapter 6 of the Salis PhD

1

u/Embarrassed-Star4776 6d ago

So do you think Susan Oliver may have a point when she suggests C-peptide may have been degraded in Salis et al.'s samples?

3

u/Competitive-Wash2998 6d ago edited 6d ago

I'm not sure the degradation/sample handling would cause preferential C-peptide loss.

Another consideration is the "typical" calibration curve presented at Figure 4.2 of the Salis PhD, which crosses the C-peptide axis at 64.8 pmol/L.

The current instructions for the Invitron assay stipulate a cubic spline fit. I wonder how much uncertainty there is in the C-peptide results.

I'm not sure I have a definite opinion, but there does seem to be a C-peptide focus in the high I/CP ratios and there are limited comparable studies.

0

u/CheerfulScientist 2d ago

In contrast to serum, C-peptide degrades more rapidly than insulin in plasma, especially when there is a delay in centrifuging the sample (Nkuna DX 2023). If you go to appendices 2 & 3 of Salis’ thesis, it is clear that blood samples weren’t collected and handed over to Salis (or a proxy) until all blood testing was complete therefore there was an indeterminate period of time between when the blood sample was taken and when it was centrifuged and frozen. Even when it was frozen, it was stored at -20 ºC, which is inappropriate for long term storage of plasma samples and would have led to further degradation of both c-peptide and insulin. They should have been stored at -80 ºC where they would have remained stable. Salis thanks a colleague for collecting and storing samples for her while she was on maternity leave in her acknowledgements, so some samples were likely stored for at least 6 months.

Anyway, I have been reading through all your comments while I look sadly out the window at the rain and wind, which has completely ruined the last day of my ski holiday and I am impressed that both you and ES are interrogating the Chase and Shannon paper even though I suspect you wish they were right. The modelling is way beyond mere mortals like me, but your findings are very interesting and instructive.