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Clinical Chemistry, Vol 42, 1147-1154, Copyright © 1996 by American Association for Clinical Chemistry
MJ Khosravi, A Diamandi, J Mistry and PD Lee
Diagnostic Systems Laboratories (Canada) Inc., Toronto, ON, Canada.
Measurement of serum insulin-like growth factor I (IGF-I) is important in assessing the growth hormone/IGF axis. Competitive immunoassay methods for IGF-I are complicated by substantial interference from IGF- binding proteins (IGFBPs) due to the relatively low ratio of specific antibody to IGFBPs in the sample, even after standard acid-ethanol sample extraction. We report of development of a noncompetitive ELISA for human IGF-I that avoids this problem by utilizing excess amounts of capture and detection antibodies. Serum samples were prepared by using an abbreviated acid-ethanol extraction method. Neutralized supernatant was added to microwells coated with IGF-I capture antibody; horseradish peroxidase-labeled detection antibody was then added, incubated for 2 h, and then developed. Compared with the "gold standard" method of acid- column chromatography, the simplified acid-ethanol extraction yields a mean +/- SD recovery of 103% +/- 5.5% despite the presence of residual IGFBPs in the extracted sample. Comparisons with a centrifugal filtration sample extraction method are also shown. The ELISA is specific for IGF-I with an absolute sensitivity of 0.03 microgram/L and inter- and intraassay CVs of 3.9-8.8% and 2.6-6.7%, respectively. The availability of a rapid IGF-I ELISA combined with a simple and reliable sample preparation procedure should facilitate clinical and research studies of this important growth factor.
The following articles in journals at HighWire Press have cited this article:
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  A. Lopez-Bermejo, J. Khosravi, C. L. Corless, R. G. Krishna, A. Diamandi, U. Bodani, E. M. Kofoed, D. L. Graham, V. Hwa, and R. G. Rosenfeld Generation of Anti-Insulin-Like Growth Factor-Binding Protein-Related Protein 1 (IGFBP-rP1/MAC25) Monoclonal Antibodies and Immunoassay: Quantification of IGFBP-rP1 in Human Serum and Distribution in Human Fluids and Tissues J. Clin. Endocrinol. Metab., July 1, 2003; 88(7): 3401 - 3408. [Abstract] [Full Text] [PDF]
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J. Khosravi, A. Diamandi, J. Mistry, and A. Scorilas Insulin-Like Growth Factor I (IGF-I) and IGF-Binding Protein-3 in Benign Prostatic Hyperplasia and Prostate Cancer J. Clin. Endocrinol. Metab., February 1, 2001; 86(2): 694 - 699. [Abstract] [Full Text]
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A. Diamandi, J. Mistry, R. G. Krishna, and J. Khosravi Immunoassay of Insulin-Like Growth Factor-Binding Protein-3 (IGFBP-3): New Means to Quantifying IGFBP-3 Proteolysis J. Clin. Endocrinol. Metab., June 1, 2000; 85(6): 2327 - 2333. [Abstract] [Full Text]
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J. Khosravi, A. Diamandi, J. Mistry, and R. G. Krishna The High Molecular Weight Insulin-Like Growth Factor-Binding Protein Complex: Epitope Mapping, Immunoassay, and Preliminary Clinical Evaluation J. Clin. Endocrinol. Metab., August 1, 1999; 84(8): 2826 - 2833. [Abstract] [Full Text]
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A. Diamandi, M. J. Khosravi, J. Mistry, V. Martinez, and J. Guevara-Aguirre Filter Paper Blood Spot Assay of Human Insulin-Like Growth Factor I (IGF-I) and IGF-Binding Protein-3 and Preliminary Application in the Evaluation of Growth Hormone Status J. Clin. Endocrinol. Metab., July 1, 1998; 83(7): 2296 - 2301. [Abstract] [Full Text]
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M. J. Khosravi, A. Diamandi, J. Mistry, R. G. Krishna, and A. Khare Acid-Labile Subunit of Human Insulin-Like Growth Factor-Binding Protein Complex: Measurement, Molecular, and Clinical Evaluation J. Clin. Endocrinol. Metab., December 1, 1997; 82(12): 3944 - 3951. [Abstract] [Full Text] [PDF]
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 M. J. Khosravi, A. Diamandi, and J. Mistry Immunoassay of insulin-like growth factor binding protein-1 Clin. Chem., March 1, 1997; 43(3): 523 - 532. [Abstract] [Full Text] [PDF]
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