Aim and objectives: To compare and evaluate the effect of sample type on vitamin D concentration in order to avoid multiple sample collection.
Materials and methods: The study was conducted in a tertiary care hospital on 40 adult subjects whose samples were for both serum vitamin D and plasma parathyroid hormone (PTH). Leftover plasma sample was utilized for vitamin D analysis. Samples were analyzed on Advia Centaur XP from Siemens Healthineers. Bland–Altman analysis and regression equation were derived to evaluate the extent of agreement and conversion between sample types.
Results and conclusion: Serum vitamin D is higher than plasma vitamin D (by 6.5 ng/mL), and it is more pronounced in samples with vitamin D greater than 20 ng/mL.
Clinical significance: It is important that lab and clinicians should be aware of the comparably large preanalytical bias introduced by changing between serum and EDTA plasma sample for vitamin D analysis. This would impact patients who are serially monitored for vitamin D supplementation.
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