Establishing preanalytical stability of vitamin A and vitamin E.

Vitamin A and Vitamin E, a group of lipid-soluble vitamins, can be degraded by photolysis and photooxidation after exposure to light. As an essential area of the preanalytical stage, inappropriate storage conditions of patient samples could lead to inaccurate results. In this study, we evaluated three of the most common preanalytical storage conditions (RT, +4°C, and -20 °C) in the workflow in the clinical laboratory setting using both clear and amber Eppendorf tubes. Analyte stability in each storage condition was tested with five patient pools. After 24 hrs at RT, a significant decrease in vitamin A and E was observed for samples stored in clear Eppendorf tubes (19.2 % and 17.9 %, for vitamin A and E, respectively), compared with samples stored in amber Eppendorf tubes (9.1 % and 7.3 %), respectively. After the specimen was stored at 4 °C for 7 days, vitamin A concentrations decreased in clear tubes by 14.7 % and in amber tubes by 12.7 %. Similarly, vitamin E concentrations decreased in both clear and amber tubes by 11.2 % and 13.4 %, respectively. Both vitamin A and vitamin E demonstrated acceptable stability in clear and amber Eppendorf tubes at -20 °C for up to 22 days. It is preferable to use amber tubes to protect vitamin A and E from light during short term storage. Storage of vitamin A and E specimens beyond 7 days should be at -20 °C.