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RELATIONSHIP BETWEEN VITAMIN D AND ALKALINE PHOSPHATASE LEVELS IN VERY LOW BIRTH WEIGHT (VLBW) INFANTS
  1. R A McCarthy1,
  2. N McCallion1,
  3. E J Molloy3
  1. 1Department of Paediatrics, National Maternity Hospital, Holles Street, Dublin, Ireland
  2. 2Department of Neonatology, Our Lady’s Hospital for Children, Crumlin, Dublin, Ireland
  3. 3Department of Paediatrics, University College Dublin, Belfield, Dublin, Ireland

Abstract

Introduction Vitamin D deficiency is increasingly recognised in neonates especially if born to high risk mothers. Term high-risk newborn infants have higher mean alkaline phosphatase (AP) concentrations than controls, indicating increased bone turnover, although values remain within the normal range. There is little research on vitamin D deficiency in VLBW infants, who are at high risk of bone disease due to osteopenia of prematurity (OP) and potentially maternal or nutritional vitamin D deficiency. We hypothesised that elevated AP levels may predict abnormal vitamin D levels in VLBW infants.

Methods Convalescent, stable VLBW infants admitted to a tertiary referral Neonatal Intensive Care Unit were eligible for inclusion if their AP was >1000 IU in routine “growing” bloods. Vitamin D levels were performed in these infants.

Results 50 VLBW infants had a convalescent AP performed in the first month of life. 32 infants with AP >1000 iu had vitamin D levels sampled of which 10 were in the normal range (>50 nmol/L). AP levels did not correlate with vitamin D, calcium or phosphate levels. Infants with normal vitamin D levels were significantly older than those who were deficient (mean±SD = 76.1±23.2 versus 49.4±25.7 days respectively).

Conclusions Due to the increased risk of OP in VLBW infants early recognition and treatment of vitamin D deficiency is vital. AP, calcium and phosphate are not adequate surrogates for OP and/or vitamin D deficiency. 69% of infants tested for vitamin D were deficient and may suggest that vitamin D levels should be performed in all VLBW at 3–4 weeks of age.

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