Abstract
BackgroundThere 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.MethodsBlood 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.ResultsMean serum 25‐OH VitD concentrations for subsequent days of storage compared with day 0 showed a significant time effect (P < .05) except for the samples on day 1 (P = .654) in non‐vortexed samples and day 2 (P = .087), 5 (P = .118) and 30 (P = .118) in vortexed samples. Comparing values for vortexed and non‐vortexed samples on the same day, serum 25‐OH VitD showed a significant difference on days 1 (P = .003), 4 (P = .037), 5 (P = .002), and 30 (P = .025). However, the maximum change value was 8.85% which was less than the known total allowable error (TEa) and reference change value (RCV) for serum 25‐OH VitD.Conclusion25‐OH VitD is pre‐analytically stable after long‐term sample storage at −20°C and can be analyzed without vortexing. This may be beneficial for both research and diagnostic laboratories.
Highlights
Vitamin D is required for normal development and bone health
Vitamin D deficiency is known to cause rickets in children and osteo‐ malacia in adults
Previous studies suggest that serum 25‐OH VitD is a stable analyte under various conditions, with no significant change in 25‐OH VitD concentration was observed under multiple freeze‐thaw cycles, light exposure, or different storage conditions
Summary
Vitamin D is required for normal development and bone health. Vitamin D deficiency is known to cause rickets in children and osteo‐ malacia in adults. 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 sta‐ bility of biological samples. Conclusion: 25‐OH VitD is pre‐analytically stable after long‐term sample storage at −20°C and can be analyzed without vortexing. This may be beneficial for both re‐ search and diagnostic laboratories
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