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August 2026


Malay. J. Biochem. Mol. Biol. (2026) 29 (2)

Page range 1-58

Regular Article 

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DOI:

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Page 10-15

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Bonnie Tang Bao Chee, Tay Siow Phing, Nurul Farhana Satar, Asri Said and Loh Huai Heng

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EVALUATION OF SAMPLE TYPES AND STORAGE EFFECTS ON VITAMIN D QUANTIFICATION BY CHEMILUMINESCENCE IMMUNOASSAY (CLIA)

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Abstract 

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Vitamin D is an essential micronutrient for bone health, and its stability in stored samples is critical for accurate clinical measurement. The effects of sample types and various storage conditions on vitamin D concentrations are still under appreciated. Therefore, this study was conducted to investigate how sample types (serum vs. plasma), storage temperatures (-30°C vs. -80°C) and storage durations (1 month, 3 months and 6 months of post-sampling) affected 25-hydroxyvitamin D [25(OH)D] concentrations. Blood samples were collected from 30 subjects, and processed into serum and plasma. The baseline concentration of 25(OH)D was immediately measured in all samples using an automated chemiluminescence immunoassay (CLIA) analyser. The samples were then aliquoted and stored at -30°C and -80°C for further re-analysis at 1 month, 3 months and 6 months of storage durations. Baseline measurements revealed a significantly higher concentration of 25(OH)D in plasma than serum (mean difference of 7.01 ng/mL; p=0.013). During frozen storage, plasma 25(OH)D concentrations declined significantly starting from the first month of storage at -30°C (p<0.001) and -80°C (p<0.001). Serum 25(OH)D exhibited long-term stability for up to six months when stored at -30°C (p=1.000) and -80°C (p=1.000). This study demonstrates that serum serves as an optimal storage medium for clinical 25(OH)D testing, particularly in studies requiring sample transportation and batch analysis, to minimise pre-analytical errors that may lead to misclassification of patients’ vitamin D status.

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