The International Reference Reagent for insulin-like growth factor-I

Area of Science:

• Biochemistry
• Endocrinology
• Pharmacology

Background:

• Insulin-like growth factor-I (IGF-I) plays a crucial role in growth and metabolism.
• Standardization of IGF-I measurements is essential for accurate clinical diagnosis and research.
• Recombinant DNA technology offers a potential source for standardized IGF-I preparations.

Purpose of the Study:

• To evaluate three recombinant DNA-derived insulin-like growth factor-I (IGF-I) preparations as candidate International Reference Reagents.
• To assess the suitability of these preparations for use in immunoassays.
• To establish a WHO International Reference Reagent for IGF-I.

Main Methods:

• An international collaborative study involving nine laboratories across four countries.
• Evaluation of three IGF-I preparations (coded 86/522, 86/720, 87/518) using immunoassay techniques.
• Comparison of dose-response curves against local standards and serum-derived IGF-I.

Main Results:

• Immunoassay dose-response curves generally did not differ significantly between preparations and local standards.
• Significant heterogeneity was observed in ampoule content estimates across laboratories.
• Preparation 86/720 showed heterogeneity via HPLC, and 86/522 had anomalous stability data.

Conclusions:

• Preparation 87/518 was established by the WHO as the International Reference Reagent for IGF-I immunoassay.
• The assigned ampoule content for 87/518 is 3.1 micrograms/ampoule.
• This reference reagent is available from the National Institute for Biological Standards and Control.