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.