Bone Abstracts

Data on the prevalence of vitamin D deficiency/insufficiency in children with haematological malignancies (HM) in Sweden are scarce. Our studies indicate that one third of children with HM had vitamin deficiency/insufficiency already at the time of diagnosis. In this study, we aimed to investigate the impact of season and age at HM onset on vitamin D status by analysing 25(OH)D levels in two different age groups: children ≤6 years of age, and children >6 years of age. We carried out a cross-sectional study including all 295 children aged <18 years who were diagnosed with HM in our institution between 1990 and 2016 and had a stored serum sample available from the time of diagnosis. All samples had been stored at –80 °C. The serum 25(OH)D levels were measured by a direct competitive immunochemiluminescent assay, with reagents from the same batch in January 2018. Serum 25(OH)D levels <25 nmol/L were considered deficient, 25–50 nmol/L insufficient, 50–75 nmol/L sufficient, and ≥75 nmol/L optimal. Clinical data (sex, age, diagnosis, date of the diagnosis) were collected from the Swedish Childhood Cancer Registry. Children ≤6 years old: This group included 163 children (83 males), 3.1% of them had vitamin D deficiency, 20.2% had insufficiency, 44.2% had sufficiency, and 32.5% had optimal levels. Linear regression indicated that season did not influence 25(OH)D levels. Children >6 years old: This group included 132 children (86 males), 10.6% of them had vitamin D deficiency, 34.8% had insufficiency, 34.1% had sufficiency, and 20.5% had optimal levels. When analyzed using unadjusted linear regression, season showed a significant influence on 25(OH)D levels. After adjusting for age and calendar year, season still had a significant impact on vitamin D levels (fall, winter and spring compared with summer, P=0.046, P<0.001, P<0.001 respectively).

Conclusion: Subnormal 25(OH)D levels are common in paediatric patients with HM already at the time of diagnosis, especially in older children. Children >6 years of age had a seasonal variation in levels of 25(OH)D, which was not found in younger children.

Disclosure: The authors declared no competing interests.