The pre-analytical stability of 25-hydroxyvitamin D: Storage and mixing effects

Abstract

Background: There is an increasing demand for serum 25-OH VitD testing globally, and this has led to the greater use of automated immunoassays. These may be more prone to non-specific interference, that is thought to be related to pre-analytical stability of biological samples. We have investigated the changes in serum 25-OH VitD concentrations that are caused by storage and mixing conditions, and if such changes are statistical, or clinically important. Methods: Blood samples were collected into plain tubes from 31 healthy donors. After separation, serum samples were stored at −20°C and analysis was carried out with and without mixing (vortexing) at different time intervals of days (0, 1, 2, 3, 4, 5, 15, and 30). All samples were analyzed using a chemiluminescent immunoassay. Results: Mean serum 25-OH VitD concentrations for subsequent days of storage compared with day 0 showed a significant time effect (P