Short- and medium-term pre-analytical stability of human serum insulin-like growth factor-1

Insulin-like growth factor-1 (IGF-1) is a peptide hormone currently lacking data surrounding its pre-analytical stability. This study aimed to investigate the impact of delaying centrifugation and analysis at different storage temperatures on the in vitro stability of IGF-1.

The study followed the Checklist for Reporting Stability Studies (CRESS). Ten healthy, adult participants were recruited to donate 40 mL of blood each. Blood was collected into serum separator tubes. Samples were aliquoted and split into two main categories i.e., immediate centrifugation (timepoint zero) and delayed centrifugation (by 8 and 24 h). These categories were further subdivided into different storage temperatures i.e., -20 °C, 4 °C, 20-25 °C and 30 °C. All measurements were conducted in duplicate on a DiaSorin LIAISON^® XL (Via Crescentino snc, Saluggia, Italy). Analysis occurred immediately after centrifugation (timepoint zero), after 8, 24, 48, 72, 168 and 672 h in the respective categories. The percentage deviation (PD) from baseline was calculated and a maximum permissible difference of ≥10.7 % (based on biological variation) was considered significant.

In our study, IGF-1 was stable for at least 72 h regardless of delay in centrifugation or storage temperature. Samples that were refrigerated were stable until 168 h (PD≤5.5 %) regardless of a delay in centrifugation. Samples that were frozen at -20 °C were stable up to 672 h (PD -1.5 %).

IGF-1 is stable up to 72 h after sampling regardless of delay in centrifugation or storage temperature. Stability may be lengthened to 7 days by refrigerating at 4 °C.