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C-Peptide Response to Glucose, 8 Specimens [15848X]
Test Code15848
CPT Codes
84681 (x8)
Preferred Specimen
1 mL serum for each timed specimen
Patient Preparation
Patients should fast 12 hours prior to collection
Minimum Volume
0.5 mL for each timed specimen
Instructions
Draw fasting specimen. Administer oral glucose solution (1.75 g/kg body weight or 75 g maximum).
Collect 1 mL serum for each timed specimen post glucose dose. All tubes must be clearly marked with time drawn. Submit all tubes with one test requisition.
Collect 1 mL serum for each timed specimen post glucose dose. All tubes must be clearly marked with time drawn. Submit all tubes with one test requisition.
Transport Container
Transport tube(s)
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 4 days
Refrigerated: 7 days
Frozen -20° C: 7 days
Frozen -70° C: Not established
Refrigerated: 7 days
Frozen -20° C: 7 days
Frozen -70° C: Not established
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Plasma
Methodology
Immunoassay (IA)
Setup Schedule
Set up: Mon-Sat a.m.; Report available: Next day
Reference Range
| Fasting: | 0.80-3.85 | ng/mL |
| 30 minutes post glucose: | 1.78-7.49 | ng/mL |
| 60 minutes post glucose: | 1.91-8.21 | ng/mL |
| 90 minutes post glucose: | 1.52-7.95 | ng/mL |
| 120 minutes post glucose: | 1.19-6.04 | ng/mL |
| 150 minutes post glucose: | 1.06-5.98 | ng/mL |
| 180 minutes post glucose: | 1.06-3.88 | ng/mL |
| 240 minutes post glucose: | 0.86-3.22 | ng/mL |
| 300 minutes post glucose: | 0.86-2.50 | ng/mL |
Clinical Significance
C-Peptide is useful in the evaluation of pancreatic beta cell function (e.g., helping distinguish type 1 from type 2 diabetes mellitus, or monitoring patients who have received islet cell or pancreatic transplants) and for determining the source of insulin in patients with hyperinsulinemic hypoglycemia. (e.g., distinguishing insulin-secreting tumors from exogenous insulin administration). It is also sometimes measured as an additional means (more resistant to hemolysis than is insulin itself) for evaluating glucose tolerance tests.
