Insulin, serum or plasma

Lab area

Clinical Biochemistry - General

Method and equipment

Equipment : Roche Cobas Pro e801

Method : Sandwich principle. Total duration of assay: 18 minutes

1st incubation: Insulin from 12 µL sample, a biotinylated monoclonal insulin‑specific antibody, and a monoclonal insulin‑specific antibody
labeled with a ruthenium complexa) form a sandwich complex.
▪ 2nd incubation: After addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via interaction of biotin and
streptavidin.
▪ The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell II M. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier.
▪ Results are determined via a calibration curve which is instrumentspecifically generated by 2‑point calibration and a master curve provided via the cobas link.

Expected turn-around time

STAT: 1 hours Urgent: 4 hours Routine: 8 hours

Specimen type

Serum, lithium heparin

Specimen requirements

250 uL

Storage and transportation

Frozen

Shipping information

The Hospital for Sick Children

Rapid Response Laboratory

555 University Avenue, Room 3642

Toronto, ON

Canada

M5G 1X8

Phone: 416-813-7200

Toll Free: 1-855-381-3212

Hours: 7 days/week, 24 hours/day

Requisition

Insulin, serum or plasma - requisition

Background and clinical significance

Insulin is a polypeptide hormone (MW 6000) composed of two nonidentical chains, A and B, which are joined by two disulfide bonds. Insulin is formed from a precursor, proinsulin (MW 9000), in the beta cells of the pancreas. In proinsulin, the A and B chains are joined by a connecting peptide, referred to as the C-peptide. Both insulin and C-peptide are stored in secretory granules of the islet cells of the pancreas and are then secreted. Immunoassays for insulin have been widely used to provide supplementary information, first, for the diagnosis of diabetes mellitus and, second, for differential diagnosis of fasting hypoglycemia to discriminate between insulinoma and factitious hypoglycemia.