Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Insulin is the principal hormone responsible for the control of glucose metabolism. It is synthesised in the β-cells of the islets of Langerhans as the precursor, proinsulin, which is processed to form c-peptide and insulin, which are secreted in equimolar amounts into the portal circulation. Secretion of insulin is mainly controlled by plasma glucose concentration and the hormone has a number of important metabolic actions. Its principal function is to control the uptake and utilisation of glucose in peripheral tissues. This and other hypoglycaemic actions, such as the inhibition of hepatic gluconeogenesis and glycogenolysis are counteracted by the hyperglycaemic hormones glucagon, adrenaline, growth hormone and cortisol. The principal clinical application of insulin measurement is in the investigation of unexplained hypoglycaemia.
Specimen container paediatric:
Serum or plasma (LiHep or EDTA)
Specimen container adult:
Serum or plasma (LiHep or EDTA)
Minimum volume paediatric:
1 mL blood
Minimum volume adult:
2 mL blood
Special requirements:
Samples should arrive in lab within 1 hour of sampling.
Fasting sample, unless part of dynamic function test, or during spontaneous hypoglycaemic episode.
Also send a sample for glucose (fluoride/oxalate).
Sample stability:
Unseparated:
2 hours
Separated:
1 day at 4 to 8°C,
6 months at -20°C
Transport requirements:
External locations: send as frozen serum/plasma.
Internal samples: send unseparated at ambient temperature to be received within 1 hour of sampling.
Availability:
Available during full access hours
Assayed weekly
Site of analysis: RVI
Interpretation:
The Mercodia Iso-insulin ELISA employs antisera with substantial cross reactivity with all commonly used insulin analogues. When used in combination with measurement of C-peptide this allows the reliable detection of exogenous Insulin administration. When samples are taken during a hypoglycaemic episode, elevated insulin concentrations in the presence of suppressed c-peptide 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).
Reference ranges:
Adult: 12 – 150pmol/L
Factors affecting result:
Haemolysis in serum or plasma may result in a degradation of Insulin which could give falsely low values.
Heterophilic antibodies can interfere with immunoassays.
Other info:
EDTA or LiHep plasma also suitable