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THE MARKER THAT MATTERS

Why C-peptide matters in T1D progression

 

BETA-CELL FUNCTION CAN BE ASSESSED BY MEASURING 
C-PEPTIDE1-4

WHAT IS C-PEPTIDE?

C-peptide is a 31-amino-acid cleaved from proinsulin within the beta cell. It is produced in equal amounts to insulin and is the clearest measure of endogenous insulin secretion.5,6

ALONG WITH GLUCOSE MONITORING AND AUTOANTIBODY SCREENING, C-PEPTIDE TESTING MAY OFFER USEFUL INSIGHT INTO BETA-CELL FUNCTION IN CLINICAL T1D1,4

Once a patient is diagnosed, C-peptide testing can identify the extent of beta-cell function1-4

C-PEPTIDE IS A WELL-ESTABLISHED SURROGATE FOR ASSESSING BETA-CELL FUNCTION6

C-peptide provides a more reliable measure of beta-cell function vs insulin1,5,8,9

C-PEPTIDE TESTING

There are multiple factors associated with the usefulness of C-peptide testing, including its reliability and options for types of tests1,5,8,9

C-PEPTIDE

Reliable measure of beta-cell function due to1,5,8,9:

  • Constant rate of clearance
  • Not being affected by exogenous insulin

INSULIN

Difficult to measure accurately due to1,5,8,9:

  • Variable rate of clearance
  • Being impacted by exogenous insulin

 

TYPES OF TESTS1,10,11

STIMULATED

Provides the most accurate picture by using a trigger, like a meal or glucagon, to provoke an insulin response

FASTING

Measures baseline production after an overnight fast

RANDOM NON-FASTING

Measures current production without regard to food intake

 

INTERPRETING C-PEPTIDE MEASUREMENTS FOR BETA-CELL FUNCTION

Since C-peptide and insulin are secreted by beta cells at a 1:1 ratio, remaining beta-cell function can be assessed by measuring C-peptide1-4

A test tube with little liquid inside; In symptomatic autoimmune T1D, clinically meaningful beta-cell function is indicated by: Stimulated C-peptide level over 0.6 ng/ML (0.2 pmol/mL*)

*Based on a conversion from 0.2 pmol/mL using the molecular weight of 3020.3 g/mol for C-peptide.1-4

 

 

*A specific test code may be required in addition to the CPT code. Please confirm which codes are required for your preferred laboratory.
†This code is provided as an example only and is not all-inclusive; appropriate codes can vary by patient, setting of care, and payer. This information is not meant to provide medical or legal advice or recommendations regarding the use of specific codes for billing purposes. The provider submitting the claim is responsible for determining the medical necessity, appropriate coding, and accuracy of claims.
CPT is the registered trademark of the American Medical Association. Other third-party marks are the property of their respective owners.
CPT=Current Procedural Terminology; T1D=type 1 diabetes.

 

MEASURING C-PEPTIDE TO ASSESS BETA-CELL FUNCTION MAY BE IMPORTANT FOR THE EVALUATION OF CLINICAL T1D3

 

References

  1. Leighton E, Sainsbury CAR, Jones GC. A practical review of C-peptide testing in diabetes. Diabetes Ther. 2017;8(3):475-487.

  2. Palmer JP, Fleming GA, Greenbaum CJ, et al. C-peptide is the appropriate outcome measure for type 1 diabetes clinical trials to preserve β-cell function: report of an ADA workshop, 21-22 October 2001. Diabetes. 2004;53(1):250-264.

  3. Pociot F. Capturing residual beta cell function in type 1 diabetes. Diabetologia. 2019;62(1):28-32.

  4. Latres E, Greenbaum CJ, Oyaski ML, et al. Evidence for C-peptide as a validated surrogate to predict clinical benefits in trials of disease-modifying therapies for type 1 diabetes. Diabetes. 2024;73(6):823-833.

  5. Maddaloni E, Bolli GB, Frier BM, et al. C-peptide determination in the diagnosis of type of diabetes and its management: a clinical perspective. Diabetes Obes Metab. 2022;24(10):1912-1926.

  6. Michels AW, Brusko TM, Evans-Molina C, et al. Challenges and opportunities for understanding the pathogenesis of type 1 diabetes: an Endocrine Society scientific statement. J Clin Endocrinol Metab. 2025;110(9):2496-2508.

  7. Sørensen JS, Johannesen J, Pociot F, et al; Danish Society for Diabetes in Childhood and Adolescence. Residual β-cell function 3-6 years after onset of type 1 diabetes reduces risk of severe hypoglycemia in children and adolescents. Diabetes Care. 2013;36(11):3454-3459.

  8. Stankute I, Verkauskiene R, Dobrovolskiene R, et al. Kinetics of C-peptide during mixed meal test and its value for treatment optimization in monogenic diabetes patients. Diabetes Res Clin Pract. 2021;178:108938.

  9. Jones AG, Hattersley AT. The clinical utility of C-peptide measurement in the care of patients with diabetes. Diabet Med. 2013;30(7):803-817.

  10. Greenbaum CJ, Mandrup-Poulsen T, McGee PF, et al; Type 1 Diabetes Trial Net Research Group; European C-Peptide Trial Study Group. Mixed-meal tolerance test versus glucagon stimulation test for the assessment of β-cell function in therapeutic trials in type 1 diabetes. Diabetes Care. 2008;31(10):1966-1971.

  11. Hope SV, Knight BA, Shields BM, et al. Random non‐fasting C–peptide: bringing robust assessment of endogenous insulin secretion to the clinic. Diabet Med. 2016;33(11):1554-1558.

  12. Flatt AJS, Greenbaum CJ, Shaw JAM, et al. Pancreatic islet reserve in type 1 diabetes. Ann N Y Acad Sci. 2021;1495(1):40-54.

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