Figure 3. Five day stability of C-peptide and insulin in whole blood stored on K⁺-EDTA and serum gel at room temperature and 4°C.

Blood taken from 5 non-diabetic volunteers assayed on the E170. The samples were stored at room temperature (top row; figures A and B) and in the fridge at 4°C (bottom row; figures C and D) at 0, 12, 24, 36, 48, 72, 96 and 120 hours before freezing at −80°C. Data presented as mean percentage of baseline at each time point, with error bars representing the 95% confidence intervals. Red lines indicate samples collected in K⁺-EDTA, blue lines indicate blood collected into serum gel.