C-Peptide, Serum
Code:9061
| Includes | C-peptide |
|---|
Analysis details
Methodology
- Electrochemiluminescence immunoassay (ECLIA)
- Chemiluminescent immunoassay (CLIA)
Expected Turnaround Time
1 day
Special Instructions
- Do not consume alcohol during the 24 hours before the blood draw.
- Fast for at least 8 hours before collection; water is allowed.
- Avoid vigorous exercise and emotional stress for the 30 minutes preceding collection.
- Do not smoke during the 3 hours before the specimen is collected.
- High-dose biotin (vitamin B7) can interfere with immunoassays; stop biotin supplements for at least 72 hours before collection.
How to use
C-Peptide, Serum (connecting peptide) is used to assess endogenous insulin secretion and beta-cell reserve. It supports differentiation of type 1 from type 2 diabetes at presentation, particularly in children and young adults, and assists in deciding when to initiate insulin therapy in type 2 diabetes with inadequate glycemic control despite maximal oral therapy. Serial measurement is applied to track residual beta-cell function in type 1 diabetes and to evaluate graft performance following islet or pancreas transplantation. The assay also contributes to the evaluation of endogenous hyperinsulinism and the diagnostic workup for suspected insulinoma.
Limitations
C-peptide is the peptide segment that links the A and B chains within proinsulin and is released in equimolar amounts with insulin when proinsulin is processed to its active form. Unlike insulin, it does not undergo substantial first-pass clearance by the liver, making peripheral C-peptide concentration a more faithful surrogate of pancreatic insulin output. The measurement is unaffected by exogenous insulin administration and is less influenced by anti-insulin antibodies than direct insulin assays. Clinically, C-peptide helps differentiate absolute insulin deficiency characteristic of autoimmune type 1 diabetes from the relative insulin deficiency combined with insulin resistance seen in type 2 diabetes. It informs prognosis at the onset of type 1 diabetes and allows longitudinal tracking of beta-cell function. The assay also documents endogenous hyperinsulinism in the evaluation of insulinoma, including cases arising in the setting of multiple endocrine neoplasia, and is used to assess graft function after islet transplantation.
| Unit | ng/mL | ||||
|---|---|---|---|---|---|
| Reference interval |
| ||||
| Indications | Workup of symptomatic hyperglycemia suggestive of type 1 diabetes (polydipsia, polyuria, weight loss, polyphagia)., Assessment of suspected type 2 diabetes or impaired glucose tolerance in overweight or obese individuals presenting with hyperglycemic symptoms., Evaluation of chronic hyperglycemia in the setting of microvascular or macrovascular complications, including diabetic retinopathy, peripheral neuropathy, diabetic foot ulcers, chronic kidney disease, coronary artery disease, and hypertension., Differentiation between type 1 and type 2 diabetes, with emphasis on newly diagnosed children and young adults., Monitoring of therapy response and residual beta-cell function in established type 1 diabetes., Decision support for starting insulin in type 2 diabetes when glycemic targets are not met on maximal oral agents., Investigation of fasting hypoglycemia due to endogenous hyperinsulinism, including suspected insulinoma with adrenergic and neuroglycopenic manifestations. |
Possible Causes of Abnormal Results
Increased levels
- chronic hepatitis
- cirrhosis
Decreased levels
- biotin supplementation (high dose)
Specimen Requirements
| Specimen | Serum |
|---|---|
| Container | Gold/Tiger Top (SST, Gel Separator) |
| Volume | 1 mL (min 0.7 mL) |
| Storage Instructions | Room temperature, Refrigerated, Frozen |
References
Chernecky C. C., Berger B. J. Laboratory Tests and Diagnostic Procedures. 5th ed. Saunders Elsevier; 2008.
Handelsman Y, et al. American Association of Clinical Endocrinologists Medical Guidelines for Clinical Practice for developing a diabetes mellitus: comprehensive care plan. Endocr Pract. 2011;17(Suppl 2):1–53.
Palmer J P, et al. C-peptide is the appropriate outcome measure for type 1 diabetes clinical trials to preserve beta-cell function: report of an ADA workshop, 21–22 October 2001. Diabetes. 2004;53(1):250–64.
Ryan E A, Paty B W, Senior P A, et al. Five-year follow-up after clinical islet transplantation. Diabetes. 2005;54(7):2060–9.
Saisho Y, Kou K, Tanaka K, et al. Postprandial serum C-peptide to plasma glucose ratio as a predictor of subsequent insulin treatment in patients with type 2 diabetes. Endocr J. 2011;58(4):315–22.