Reference change values for insulin and insulin-like growth factor binding protein-1 (IGFBP-1) in individuals with varying degrees of glucose tolerance

Abstract

Background. The reference change value (RCV) is an important parameter of biological variation used to assess the significance of differences between consecutive results obtained in a single individual. This study evaluated the RCV for insulin-like growth factor binding protein-1 (IGFBP-1) and fasting serum insulin (FSI) in individuals with different degrees of glucose tolerance. Methods. IGFBP-1 and FSI concentrations were measured in 33 fasting subjects who had two blood samples taken 10 days apart. Subjects were distributed in the following categories: Normal glucose tolerance (NGT), n = 15, impaired fasting glucose (IFG), n = 9 and impaired glucose tolerance (IGT), n = 9. Results. The RCV values for IGFBP-1 were 59.9%, 83.2% and 93.0% and for FSI were 68.5%, 79.0% and 93.4% for subjects with NGT, IFG and IGT respectively. Conclusions. The RCVs for IGFBP-1 and FSI increase with deteriorating glucose tolerance. When monitoring IGFBP-1 and FSI, changes in concentrations should be interpreted using glycaemic category-specific RCV values.

Key Words::

• IGFBP-1
• insulin
• intra-individual variation
• CVi
• reference change value
• RCV

Acknowledgements

The authors acknowledge the unlimited support received from King Abdullah International Medical Research Center (KAIMRC) of the National Guard Health Affairs, Saudi Arabia.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the article.