Test Details

• Discipline:

  Biochemistry

  Biochemistry

• Specimen Container Adult:

  Serum or plasma (LiHep or EDTA)

  Serum or plasma (LiHep or EDTA)

• Specimen Container Paediatric:

  Serum or plasma (LiHep or EDTA)

  Serum or plasma (LiHep or EDTA)

• Minimum Volume Adult:

  1 mL blood

  1 mL blood

• Minimum Volume Paediatric:

  1 mL blood

  1 mL blood

• Special Requirement:

  Samples should be separated within 6 hours of sampling.

  Fasting, unless part of dynamic function test, or during spontaneous hypoglycaemic episode.

  Also send glucose sample (fluoride/oxalate).

  Samples should be separated within 6 hours of sampling.

  Fasting, unless part of dynamic function test, or during spontaneous hypoglycaemic episode.

  Also send glucose sample (fluoride/oxalate).

• Sample Stability:

  Unseparated: 6 hours
  Separated:3 days at 2-8°C, 2 months at -20°C

  Unseparated: 6 hours
  Separated:3 days at 2-8°C, 2 months at -20°C

• Transport Requirements:

  External locations: send as frozen serum/plasma.

  Internal samples: send unseparated at ambient temperature to be received within 6 hour of sampling.

  External locations: send as frozen serum/plasma.

  Internal samples: send unseparated at ambient temperature to be received within 6 hour of sampling.

• Interpretation:

  When samples are taken during a hypoglycaemic episode, suppressed c-peptide concentrations in the presence of elevated insulin concentrations indicate exogenous insulin administration. Where both i...

  When samples are taken during a hypoglycaemic episode, suppressed c-peptide concentrations in the presence of elevated insulin concentrations indicate exogenous insulin administration. Where both insulin and c-peptide are not appropriately suppressed, this indicates endogenous hyperinsulinism (e.g. due to the presence of an insulinoma or sulphonylurea administration). The insulin assay used in Newcastle has broad specificity and detects commonly used insulin analogues.
  
  Measurement of c-peptide may be useful in the classification of type 1/type 2 diabetes where there is uncertainty. Utility is greatest 3-5 years after diagnosis when persistence of substantial c-peptide production suggests type 2 or monogenic diabetes. During the first 3-5 years there is considerable overlap in c-peptide concentrations between type 2 and type 1 diabetes, however absent c-peptide at any time confirms absolute insulin requirement regardless of aetiology.
  As the kidney is the major site for C-peptide metabolism, patients with severe renal insufficiency may have abnormally high circulating C-peptide levels.

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• Reference Ranges:

  Adult: 0.34 - 1.80 nmol/L

  Adult: 0.34 - 1.80 nmol/L

• Factors Affecting Result:

  N.B. Heterophilic antibodies can interfere with immunoassays.

  N.B. Heterophilic antibodies can interfere with immunoassays.

• Other Info:

  EDTA and LiHep plasma also suitable

  EDTA and LiHep plasma also suitable

• Routine Contact Name:

  Duty Biochemist

• Routine Telephone:

  Freeman: 0191 244 8889

  RVI: 0191 282 9719

  Freeman: 0191 244 8889

  RVI: 0191 282 9719

• Routine Email:

  nuth.dutybiochemist@nhs.net

• Specialist Test:

  Yes

  Yes

• Specialist Contact Name:

  Endocrine Lab

  Endocrine Lab

• Specialist Telephone:

  0191 282 4025

  0191 282 4025