Insulin is a polypeptide hormone that regulates carbohydrate metabolism. Apart from being the primary effector in carbohydrate homeostasis, it has effects on fat metabolism and it can change the liver's ability to release fat stores. 

Insulin is involved in: control of cellular intake of glucose in muscle and adipose tissue, increase of DNA replication and protein synthesis, modification of the activity of numerous enzyme (allosteric effect), increased glycogen, fatty acid synthesis, amino acid uptake, decreased proteinolysis, lipolysis, gluconeogenesis.  

Beta cells release insulin in a glucose-dependent way. 

In most humans blood glucose levels varies from about 70 mg/dl to perhaps 110 mg/dl (3.9 to 6.1 mmol/l) except shortly after eating when the blood glucose level rises temporarily. This homeostatic effect is the result of many factors, of which hormone regulation is the most important.

There are several conditions in which insulin disturbance is pathologic: diabetes mellitus, insulinoma, metabolic syndrome and polycystic ovary syndrome. There are two types of diabetes mellitus: type 1 (autoimmune-mediated destruction of insulin producing beta cells in the pancreas resulting in absolute insulin deficiency), and type 2 (multifactor syndrome with combined influence of genetic susceptibility and influence of environmental factors, the best known being obesity, age, and physical inactivity, resulting in insulin resistance in cells requiring insulin for glucose absorption. This form of diabetes is strongly inherited). In both cases the insulin production must be increased by medication or delivering insulin by oral or by intravenous method. 

The quantitative determination of insulin can help to determinate the dose to delivery.

Intended Use

Direct immunoenzymatic colorimetric method for quantitative determination of Insulin in human serum or plasma.

Principal of Assay

The Insulin ELISA test is based on simultaneous binding of human insulin by two monoclonal antibodies, one immobilized on microwell plates and the other conjugates with horseradish peroxidase (HRP).  After incubation, the bound/free separation is performed by a simple solid-phase washing, then the TMB-Substrate solution (TMB) is added. After an appropriate time has elapsed for maximum color development, the enzyme reaction is stopped and the absorbancies are determined. The insulin concentration in the sample is calculated based on a series of standard. The color intensity is proportional to the insulin concentration in the sample.

Specific Performance Characteristics

Intra Assay Variation

Within run variation was determined by replicate determination (16x) of two different control sera in one assay. The within assay variability is 2 %.

Inter Assay Variation

Between run variation was determined by replicate measurements of three different control sera in 2 different lots. The between assay variability is 6 %.

Specificity

The cross reaction of the antibody calculated by deriving a ratio between dose of interfering substance to dose of Insulin needed to produce the same absorbance: Insulin     - 100%
Proinsulin - n.d.
C-Peptide - n.d.

Sensitivity

The lowest detectable concentration of Insulin that can be distinguished from standard 0 is 2 µIU/ml at the 95 % confidence limit.

Correlation with RIA

The NovaTec Insulin ELISA was compared to another commercially available Insulin assay. 9 serum samples of were analysed according in both test systems.  The linear regression curve was calculated y = 1,1045 x - 2.9851 r = 0.98 (r2 = 0.96)  

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