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

BACKGROUND

Vitamin D supplementation is common practice for neonates and infants due to limited stores of vitamin D at birth. Although not commonly encountered, vitamin D toxicity can occur due to over-supplementation. However, toxic concentrations are often not included in method validation experiments, and assays often are not validated in the neonatal population.

METHODS

We compared serial 25 hydroxy vitamin D [25(OH)D] measurements in pre-term neonates receiving 25(OH)D supplementation and identified 12 patients wherein concentrations of 25(OH)D were above 50 ng/mL (125 nM) that required additional investigations as the 25(OH)D results did not match the clinical picture. Available samples were compared across 4 immunoassay platforms (LIAISON XL, Roche Cobas e602, Abbott Alinity i, and Siemens Centaur XP) and LC-MS/MS.

RESULTS

Concentrations of 25(OH)D observed on one individual immunoassay platform (LIAISON XL) fluctuated substantially between subsequent blood draws in select neonates with elevated concentrations. Serum samples from these patients showed variable agreement between LC-MS/MS and other immunoassay platforms. These fluctuations were not explained by the presence of 3-epimer-25(OH)D or 24,25(OH)2D.

CONCLUSIONS

Although we were unable to identify a cause for the variable elevated results, our findings suggest that neonatal 25(OH)D measurements alone should not be used for assessment of nutritional monitoring, and that clinical correlation and other laboratory parameters including ionized calcium should be considered.

Growth and nutrient intakes of human milk-fed preterm infants provided with extra energy and nutrients after hospital discharge

OBJECTIVES

The purpose of this pilot study was to determine whether mixing a multinutrient fortifier to approximately one half of the human milk fed each day for a finite period after discharge improves the nutrient intake and growth of predominantly human milk-fed low birth weight infants. We also assessed the impact of this intervention on the exclusivity of human milk feeding.

METHODS

Human milk-fed (> or = 80% feeding per day) low birth weight (750-1800 g) infants (n = 39) were randomly assigned at hospital discharge to either a control or an intervention group. Infants in the control group were discharged from the hospital on unfortified human milk. Nutrient enrichment of human milk in the intervention group was achieved by mixing approximately one half of the human milk provided each day with a powdered multinutrient human milk fortifier for 12 weeks after discharge. Milk with added nutrients was estimated to contain approximately 80 kcal (336 kJ) and 2.2 g protein/100 mL plus other nutrients. Intensive lactation support was provided to both groups.

RESULTS

Infants in the intervention group were longer during the study period, and those born < or = 1250 g had larger head circumferences than infants in the control group. There was a trend toward infants in the intervention group to be heavier at the end of the intervention compared with those in the control group. Mean protein, zinc, calcium, phosphorus, and vitamins A and D intakes were higher in the intervention group.

CONCLUSIONS

Results from this study suggest that adding a multinutrient fortifier to approximately one half of the milk provided to predominantly human milk-fed infants for 12 weeks after hospital discharge may be an effective strategy in addressing early discharge nutrient deficits and poor growth without unduly influencing human milk feeding when intensive lactation support is provided.