25 May 2021
by Jinny Jeffery, Roanna George

Measurement of serum c-peptide in patients following simultaneous pancreas and kidney (SPK) transplants

Jinny Jeffery, Roanna George

Measurement of c-peptide in patients following simultaneous pancreas and kidney (SPK) transplant

Jinny Jeffery and Roanna George

Derriford Combined Laboratory, Derriford Hospital, Plymouth. PL6 8DH.

Aim of Study

Type I diabetes patients with end stage renal failure are suitable candidates for simultaneous pancreas and kidney (SPK) transplantation. C-peptide is used to monitor graft function. This study aimed to look at biological variation and determine a reference interval for c-peptide in SPK patients.

Methods

37 SPK transplant patients were identified from the laboratory database (18 female and 19 male). Patients with failed transplants as defined by a serum creatinine over 200 umol/L or a HbA1c ≥48 mmol/mol or clinical details of failed transplant/pancreatectomy were excluded (6 females and 5 males). 347 c-peptide results (Immulite 2000 XPi assay) from 26 patients following successful SPK transplantation were obtained from the laboratory database. This data was used to generate a reference interval from the 2.5th to 97.5th percentiles using Analyse-it for Microsoft Excel. 15 patients had 10 or more c-peptide results enabling a review of the intra-individual biological variation for c-peptide which was displayed graphically.

Results

For SPK patients a reference interval for c-peptide of 441 – 3068 pmol/L was obtained. In order to quote a meaningful value for intra-individual biological variation, there is an assumption that the individual variation is the same for all patients, but this is not the case for c-peptide concentrations in SPK transplant patients.

Conclusions

The quoted referral laboratory reference interval for c-peptide for a healthy fasting individual with normal blood glucose is 350-1800 pmol/L.  For SPK patients a reference interval of 441 – 3068 pmol/L may be more appropriate. The higher upper limit suggests that some of these patients may have a degree of insulin resistance. The intra-individual biological variation for c-peptide in samples collected from SPK patients with successful transplants is variable from patient to patient.

Related topics

Authors

Jinny Jeffery

Clinical Scientist, Derriford Combined Laboratory, Derriford Hospital

Roanna George

Derriford Combined Laboratory, Derriford Hospital