Influence of biological sample pre-analytical manipulation for fat-soluble vitamin analysis

Objective: Determine how sample handling affects nutrient analysis of fat-soluble vitamins and minerals. Materials and methods: In experiment 1, blood was collected in either plasma or serum blood tubes and exposed to 4 hours of light or wrapped in aluminum foil to protect from light. In experiment 2, blood was collected at hours 0, 1, 2, 3, 4, 6, and 12 after the consumption of feed. In experiment 3, vitamins and minerals were assessed in varying degrees of hemolyzed blood samples. Experiment 4 evaluated liver samples exposed to various temperatures for up to 12 hours. In experiment 5, serum and liver samples were processed the day of, 1 day after, or 2 days after collection and subsequent placement into coolers with icepacks. Results: There was a significant difference (P < .05) for the interaction of tube type and light exposure for vitamin D (25-hydroxyvitamin D3) and a tendency (P < .10) for a tube type and light exposure interaction for vitamin A (retinol). Experiment 2 found serum vitamin concentrations changed post feed consumption both linearly and quadratically. Alpha-tocopherol peaked at 4 hours post meal consumption, whereas retinol peaked at 6 hours. In experiment 3, the degree of hemolysis affected (P < .05) nutrient concentration. Experiment 4 and 5 showed no differences (P > .05) in degradation of retinol and alpha-tocopherol. Implication: As many pre-analytical factors can affect laboratory results, care must be taken when collecting, handling, and storing samples for diagnostic analysis of vitamins and minerals.