Analytical Unreliability of 25 Hydroxy Vitamin D Measurements in Pre-Term Neonates

Area of Science:

• Neonatal Medicine
• Clinical Chemistry
• Laboratory Science

Background:

• Vitamin D supplementation is standard for neonates and infants.
• Vitamin D toxicity is rare but can occur from over-supplementation.
• Assays for vitamin D are often not validated for the neonatal population.

Purpose of the Study:

• To compare serial 25-hydroxy vitamin D [25(OH)D] measurements in preterm neonates.
• To investigate discrepancies between immunoassay platforms and LC-MS/MS for elevated 25(OH)D levels.

Main Methods:

• Compared serial 25(OH)D measurements in preterm neonates with elevated levels (>50 ng/mL).
• Evaluated 4 immunoassay platforms (LIAISON XL, Roche Cobas e602, Abbott Alinity i, Siemens Centaur XP) against LC-MS/MS.
• Investigated potential causes for fluctuations, including 3-epimer-25(OH)D and 24,25(OH)2D.

Main Results:

• One immunoassay platform (LIAISON XL) showed substantial fluctuations in 25(OH)D concentrations in select neonates.
• Variable agreement was observed between LC-MS/MS and other immunoassay platforms.
• Fluctuations were not attributed to 3-epimer-25(OH)D or 24,25(OH)2D.

Conclusions:

• Neonatal 25(OH)D measurements alone may not be sufficient for nutritional assessment.
• Clinical correlation and other laboratory parameters (e.g., ionized calcium) are recommended.
• Further investigation is needed to understand the cause of assay variability.