Serum insulin concentration in horses: Effect of storage and handling.

Serum insulin concentration is commonly measured during investigation of suspected endocrinopathic disease in horses, but immediate analysis is frequently unavailable. The aim of this study was to examine the effect of storing samples at room temperature for 72 h as serum and as whole blood, compared to immediate separation and freezing. Samples from 14 horses were evaluated. Correlation was excellent for all comparisons (≥0.992). Bland-Altman plots revealed a negative bias (mean difference 2.16 µIU/mL) in samples stored as whole blood compared to serum, but this difference was not considered clinically significant. At two commonly used diagnostic cut-offs, there was no effect of storage on result. This study indicates that storage at room temperature for 72 h, either as serum or whole blood, has minimal effect on measured serum insulin concentration in horses.