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IGF-I, Non-Extraction

hreynolds at uh.edu hreynolds at uh.edu
Fri Jun 14 13:05:40 EST 1996

DSL (Diagnostic Systems Laboratories, Inc.) is pleased to introduce the 
NEW Non-Extraction IGF-I IRMA and ELISA kits for quantifying IGF-I in 
serum and plasma without the necessity of performing time-consuming and 
equipment-intensive extraction procedures.  The Non-Extraction IGF-I 
assay is 510(k) cleared for marketing for in vitro diagnostic use as an 
aid in the diagnosis of growth-related disorders.   
IGF-I is a 7.6 kDa, 70 amino acid peptide that mediates the actions of 
growth hormone.  It is secreted by the liver and several other tissues 
and is postulated to have mitogenic and metabolic actions at or near the 
sites of synthesis.   IGF-I appears in the peripheral circulation 
primarily in a high molecular weight complex with IGF-binding protein-3 
and acid-labile subunit (ALS).  A smaller proportion of IGF-I may 
circulate in association with other IGF-binding proteins.  Approximately 
2-4% of the total IGF-I may circulate unbound.

The IGF-I assays are useful in the diagnosis of growth-related disorders. 
Abnormally low IGF-I levels may be a diagnostic indicator of growth 
hormone deficiency.  Conversely, elevated IGF-I levels may be indicative 
of growth hormone excess.  Direct testing of growth hormone may be 
clinically unreliable due to its episodic release from the pituitary and 
relatively short half-life in the circulation, whereas IGF-I levels 
remain relatively stable throughout the day. 

Immunoassay of IGF-I may be complicated by the presence of the high 
affinity binding proteins in the sample.  Historically, it has been 
necessary to separate the IGFs from the binding proteins prior to 
assaying for IGF-I.  The traditional extraction procedures, including 
chromatography, multiple acidification and neutralization steps, and 
centrifugation to prepare the samples are no longer required when using 
the DSL Non-Extraction IGF-I assays.  The specimens are simply diluted in 
the sample diluent provided and allowed to equilibrate at room 
temperature for 30 minutes.

The DSL assay kits utilize a two-site antibody system with highly 
specific antibodies directed against the human insulin-like growth 
factor-I peptide.  No cross-reactivity with IGF-II is exhibited, and no 
interference results from the addition of insulin, proinsulin, or growth 
hormone  at concentrations of 1 µg/tube.  

The DSL ACTIVE Non-Extraction IGF-I IRMA is a 100 tube kit featuring the 
convenience of an antibody-coated tube format and a total assay 
incubation time of only 2 hours.  The DSL ACTIVE Non-Extraction IGF-I 
ELISA is a 96-well microtitre plate assay featuring a total assay 
incubation time of 2.5 hours.

Both assays are calibrated using the World Health Organization 
international reference preparation for IGF-I immunoassay (code 87/518). 
The assays feature an extended standard range of 8 - 1000 ng/mL.  The 
absolute sensitivity of the IGF-I IRMA kit is 0.04 ng/mL, and the 
absolute sensitivity of the ELISA is 0.03 ng/mL.  Both kits include two 
levels of controls.

In addition to the ACTIVE Non-Extraction IGF-I IRMA and ELISA kits, DSL 
offers a full range of immunodiagnostic test kits and reagents for 
studies related to disorders of the growth hormone-IGF axis, an extensive 
line of assays for the studies of bone and mineral metabolism, a  
complete line of assays for fertility and reproductive function, androgen 
assessment, and more.
For more information regarding the ACTIVE Non-Extraction IGF-I IRMA and 
ELISA kits (catalog numbers DSL-2800 and DSL-10-2800, respectively) as 
well as other DSL products and services, contact the DSL Customer 
Assistance Center in Webster, TX,  USA by phone 800.231.7970 or 
713.332.9678, by fax 713.338.1895, or by e-mail mktg at dslabs.com

Diagnostic Systems Laboratories
445 Medical Center Blvd.
Webster, TX  77598

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