C-Peptide, Serum

Casandra

Casandra Test Code MC38183Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID CPRCPT Code 84681

Clinical Use

Use

The C-Peptide, Serum test is utilized in the diagnostic workup of hypoglycemia by evaluating factitious hypoglycemia due to surreptitious administration of insulin, as well as possible insulinoma. It serves as a surrogate measure for the presence or absence of physiological suppressibility of endogenous insulin secretion during the C-peptide suppression test. Additionally, it is crucial for assessing insulin secretory reserve in diabetic patients with insulin autoantibodies or undergoing insulin therapy. This includes monitoring pancreatic and islet cell transplant function and evaluating immunomodulatory therapy aimed at slowing the progression of preclinical or early-stage type 1 diabetes mellitus.

Special Instructions

Patients must fast for 8 hours before specimen collection. They should also avoid taking multivitamins or dietary supplements that contain biotin, including hair, skin, and nail supplements, for 12 hours before specimen collection. When collecting the specimen, use a serum gel tube if possible, with the red top tube as an acceptable alternative. Following collection, centrifuge and aliquot the serum into a plastic vial within 2 hours.

Limitations

Significant hemolysis can result in artifactually lower C-peptide levels, potentially leading to specimen rejection. Mild hemolysis can moderately affect C-peptide values. The assay has a cross-reactivity higher than 20% between C-peptide and proinsulin, with no significant cross-reactivity with other pancreatic islet cell or neuroendocrine peptides. Very high C-peptide levels (>180 ng/mL) may cause artifactual low measurements due to the hook effect. In cases of high antibody titers against ruthenium or streptavidin, interference could occur. Caution should be exercised in interpreting results when high C-peptide levels or interference is suspected.

Test Details

FDA Approved