Biological variation in fasting serum insulin-like growth factor binding protein-1 (IGFBP-1) among individuals with a varying glucose tolerance.

OBJECTIVE: To evaluate the biological variation of serum insulin-like growth factor binding protein-1 (IGFBP-1) in individuals with different degrees of glucose tolerance. RESEARCH DESIGN AND METHODS: IGFBP-1 was measured in 42 fasted subjects with: normal glucose tolerance (NGT=15), impaired fasting glucose (IFG=9), impaired glucose tolerance (IGT=9) and type 2 diabetics (DM=9). Short- and long-term reproducibility was determined for IGFBP-1.
RESULTS: The longer-term reproducibility (CV) of serum IGFBP-1 was 20.9%, 29.5%, 33.1% and 48.0% for subjects with NGT, IFG, IGT and DM respectively. The results for the short-term serum IGFBP-1 yielded CVs for these same respective categories of 8.2%, 16.1%, 29.2% and 13.8%.
CONCLUSIONS: IGFBP-1 measurement was least variable in NGT individuals over both long-term and short-term intervals and variability increased with deteriorating glucose tolerance. Due to its biological variation, IGFBP-1 serum level is more reliable in normal subjects than in individuals with type 2 diabetes.