Re: abstract

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Posted by Celsus on 13:12:34 2012/08/13

In Reply to: abstract posted by JoeC

In Faustman's last scientific journal publication (1) prior to the recent abstract, all she claims is that her improved technique for identifying micro-production of c-peptide (detection limit of 1.5 pmol/L) could permit the identification of those type 1 diabetics who "may benefit from intervention to preserve beta-cell function or to prevent complications." That is the view stated in the article's abstract, though the conclusion expands this a bit to the ambition to identify those patients who "may benefit from treatment to retain or enhance beta cell function."

In her latest abstract, Faustman reports transient c-peptide increases around 3.5 pmol/L in type 1 diabetics treated with BCG, but to keep this in perspective, it must be appreciated that normal c-peptide levels range between 260 pmol/L and 1320 pmol/L, so an increase from 60.3 (the mean c-peptide level in diabetics Faustman reported in her previous study) to 64 is not going to allow patients independence from exogenously injected insulin. Of course, this is only a proof-of-principle study, so very much higher doses of BCG, if tolerated (and it does have side-effects), may produce meaningful increases in c-peptide and endogenous insulin output. But it may also be the case that the destruction of the beta cells which has already occurred limits the extent to which their output can be increased, regardless of reduction in the degree of autoimmunity. For now the question remains open.

But even if this very small increase in residual c-peptide levels (and thus of internal insulin production) could be much more significantly improved, not all type 1 diabetics could benefit from this intervention, even by Faustman's own calculations. The micro-levels of c-peptide production she can detect become increasingly undetectable with longer disease duration, and there would be nothing to boost in those with no remaining c-peptide production. For 0 to 5 years disease duration, residual c-peptide production can be detected in 80% of patients; at 6-10 years, this falls to 60%; at 11 to 30 years, this falls to 40%; and at 41 years and beyond, to 10%. So as a rule of thumb, the treatment would only be likely (50%+) to benefit patients up to around a decade of disease duration. Her latest study showed patients with 15 years disease duration benefiting, but by her previous results this would not be possible in the majority of such long-duration cases.

(1) L. Wang, et al, "Persistence of Prolonged C-Peptide Production in Type 1 Diabetes," Diabetes Care, 35 (3) 465 (2012).

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