Endocrine Abstracts

Background: MBDP describes inadequate mineralisation of bones in the preterm infant. Traditionally, neonatologists have used a raised ALP and low phosphate to diagnose MBDP, with phosphate supplements as first-line treatment. An alternative management approach, published by Chinoy et al (2019), recommended PTH and vitamin D in the routine work-up.

Objectives: We undertook a review of data across two neonatal intensive care units:

• to report the incidence of MBDP defined by biochemical markers on routine blood testing of high-risk infants

• to determine the frequency of PTH and vitamin D measurement in infants meeting biochemical criteria for MBDP

• to report the incidence of MBDP related fractures

Methods: Infants <30 weeks gestation or <1500 grams, admitted for >28 days between 01/01/2015 and 31/12/2019 were included. Blood results for the duration of their admission were reviewed. Biochemical MBDP was defined as ALP >500IU/l and either phosphate <1.8 mmol/l or corrected calcium <2.2 mmol/l. Infants with a MBDP related fracture were identified from BadgerNet.

Results: A total of 809 infants were identified over a 5-year period; 424 met biochemical criteria for MBDP (52.4%). PTH was measured in 30 infants (7%); 24 had a maximum level >10 pmol/l. Vitamin D was measured in 136 infants (32%); 3 had a level <25 nmol/l, 28 had a level 25-50 nmol/l and 105 had a level >50 nmol/l. There were 4 documented fractures (1 humeral and 3 rib fractures).

Conclusions: PTH and vitamin D were measured in a minority of infants meeting biochemical criteria for MBDP. When it was measured, 80% had a raised PTH level, which would favour calcium supplementation over further phosphate provision. Treatment could be improved by targeted measurement of these markers. Whilst the majority of infants were vitamin D replete, a significant minority may have benefited from supplementation. The documented incidence of fracture related to biochemical MBDP was 1%. This suggests few babies suffered immediate severe effects of their MBDP, which may mean that the implementation of new guidance is met with scepticism. However, further research is required to explore the effects of MBDP on these infants’ short- and long-term outcomes.