ESPE Abstracts

Background: A quarter of young adults with cystic fibrosis (CF) may have osteoporosis. However, children with CF do not seem to have an increased risk of fractures.

Objective: We aimed to examine the factors that may determine longitudinal changes in bone mineralisation in children with CF.

Method: 101 children (51 females) had DXA performed and the data were expressed as expected bone mineral content for bone area SDS (BMCSDS). Of them, 49 children had a second DXA, 24 had three DXA, during the 10-year period. Markers of disease, anthropometry, bone biochemistry and DXA parameters were collected retrospectively. Vitamin D deficiency was defined as levels <50 nmol/l and insufficiency as levels between 50 and 72.5 nmol/l.

Results: Median age at baseline was 12 years (range 8–18). 17 children (35%) were vitamin D deficient on one occasion, 18 (37%) on two occasions and 1 (2%) was deficient on three occasions. 18 children (37%) were vitamin D insufficient on one occasion, 5 (10%) in two occasions and 1 (2%) on three occasions. PTH status has worsened for seven children (14.3%), if the value changed from ≤7.5 to >7.5 pmol/l at the next assessment. PTH was considered static in 79.6% children. Baseline LS BMCSDS in the 101 children, was >0.5 in 13.9% patients; was between −0.5 and 0.5, in 51%; while 35% had SDS ≤−0.5. Median LS BMCSDS decreased from baseline to subsequent assessments (−0.3; −0.4; and −0.5; P=0.053). Assessment of factors that may influence bone mineralisation change by ANOVA, the longer the time between DXA assessments, the higher the likelihood of decreased BMC. Children with worsened BMC had lower FEV1%, had a lower BMI SDS, and a higher chance to have a low vitamin D associated with high PTH.

Conclusion: Bone mineralisation as assessed by DXA decreases with time in children with CF. Lower FEV1%, poorer nutritional status and low vitamin D with high PTH were factors found to be associated with worsening BMC.