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 < .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. 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 research and diagnostic laboratories.

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Throughout this study, functional, aesthetic, and dimensional stability properties of knitted blended fabrics were experimentally presented. An experimental work was introduced to examine. In order to investigate the loop length of the knitted fabrics and the polyester blending ratio on bursting, air permeability, pilling resistance and shrinkage ratio of knitted fabrics, thirty fabric samples were knitted with three loop length, five levels of polyester ratios for single jersey and rib knit structures. Analysis of variance and regression analysis were used to detect the influence of loop length and polyester content on knitted fabric properties. The findings of this study revealed that independent variables under study have a massive influence on the functional and aesthetic properties of the knitted blended fabrics.