The utility of the C-peptide in the phenotyping of patients candidates for pancreas transplantation.

It is not unusual for simultaneous pancreas and kidney transplantation (SPK) to be performed in patients with type 2 diabetes (T2D), clinically classified as having type 1 diabetes (T1D). C-peptide determination is useful to identify these patients. We describe the prevalence and characteristics of patients with C-peptide levels >3 ng/mL, classified with T2D in 172 patients referred for SPK from 1998-2006. Nine patients (5.2%) fulfilled this criteria (mean free C-peptide 9.08 ng/mL) and were older at diabetes onset (23.5 vs. 12 yr, p < 0.001) and at assessment (42.2 vs. 37.6 yr, p = 0.047) with shorter time between diabetes onset and renal failure (17.8 vs. 22.7 yr, p = 0.3) compared with T1D patients (mean free C-peptide 0.24 ng/mL). In our experience the prevalence of T2D in candidates for SPK is not negligible. Despite some clinical differences with T1D these T2D patients can phenotypically be confounded with T1D in the absence of C-peptide determination.