Comment on Sims et al. Proinsulin Secretion Is a Persistent Feature of Type 1 Diabetes. Diabetes Care 2019;42:258–264

Due to our shared interest in this topic, we were eager to read the recent article by Sims et al. (1). We agree with the authors that proinsulin (PI) secretion can occur in individuals with long-standing type 1 diabetes (T1D), even in the absence of measurable serum C-peptide (2). However, our work is discordant with the observations of the authors, and we think it is important to understand the differences. We have previously reported (2) a 16% prevalence of PI secretion in the same T1D Exchange cohort, which is significantly less than the 89.9% reported by Sims et al. (1). In addition, we have similarly completed mixed-meal tolerance …