Measurement of insulin-like growth factor-1 and insulin-like growth factor binding protein-3 after delayed separation of whole blood samples.

OBJECTIVES: Epidemiological studies benefit from unbiased blood specimens collected with minimal cost and effort of blood collection and storage. We evaluated the stability of IGF-1 and IGFBP-3 in whole blood samples stored at room temperature to justify delays in blood processing. DESIGN AND METHODS: Total IGF-1 and IGFBP-3 levels were measured in EDTA plasma (n=12), heparin plasma (n=12) and serum (n=10) samples of healthy volunteers after blood processing delays up till 14 days. Stability of measured IGF-1 and IGFBP-3 levels was tested by paired t-test and a linear mixed effect model.
RESULTS: Longitudinal analysis showed that IGF-1 levels were not significantly affected by blood processing delays in EDTA tubes (p=0.18) and IGFBP-3 levels were marginally stable (p=0.06). In heparin plasma and serum, however, IGF-1 increased over time of delayed processing and IGFBP-3 levels tended to decrease (p<0.01).
CONCLUSION: Total IGF-1 and IGFBP-3 levels are stable in whole blood collected in EDTA tubes at room temperature up till 7 days, allowing a delay in blood processing to reduce costs in large multi-center studies.