C-PEPTIDE
Test:
179
CPT:
84681
Synonyms
1-Connecting Peptide
2-Insulin C-Peptide
3-Proinsulin C-Peptide
Special Instructions
Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient’s course of therapy. This procedure does not provide serial monitoring; it is intended for one-time use only. If serial monitoring is required, please use the serial monitoring number 480108 to order.
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Expected Turnaround Time
Within 1 day
Specimen Requirements
Specimen
Within 1 day
Volume
0.8 mL
Minimum Volume
0.3 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube or gel-barrier tube
Collection
If a red-top tube is used, transfer separated serum to a plastic transport tube. Avoid hemolysis.
Storage Instructions
Refrigerate
Causes for Rejection
Citrate plasma specimen
Test Details
Use
The principal use of C-peptide is in the evaluation of hypoglycemia. Patients with insulin-secreting neoplasms have high levels of both C-peptide and endogenous insulin; in contrast, patients with factitious hypoglycemia will have low C-peptide levels in the presence of elevated (exogenous) serum insulin. C-peptide is also useful in evaluating residual beta-cell function in insulin-dependent diabetics, many of whom have antibodies that interfere with insulin assays. Glucagon-stimulated C-peptide concentration has been shown to be a good discriminator between insulin-requiring and non−insulin-requiring diabetic patients. The diagnosis of islet cell tumor is supported by elevation of C-peptide when plasma glucose is low.