Bone Abstracts

Objectives: Low bone mineral density (BMD) is reported frequently in adult cystic fibrosis (CF) patients but the data is less consistent for children and adolescents. The aim of our study is to describe bone mineral density (BMD) in a group of children over a period of 10 years and to determine if BMD is related to vitamin D level, calcium intake, lung function, height and age.

Methods: A retrospective review of 123 DXA scans conducted in 50 children with CF was evaluated (Lunar, DPXL/ PED, WI, USA). To adjust for body size we calculated apparent BMD (BMAD) of DXA reports using the Dutch reference database¹ as recommended by the International Society for Clinical Densitometry (ISCD)². Subsequent DXA scans were repeated at 1, 2 or 3 years depending on severity. Nutritional status (BMI) pulmonary status (FEV1%), vitamin D, calcium intake (5 day food diary) and age were evaluated as potential correlates of BMAD. Minitab statistical package (version 14) was used to analyse the data.

Results: Fifty children (24 girls) with mean age 12.8±2.1 (S.D.) years at time of first DXA scan were included. BMAD was normal (DXA Z-score of >−1) in 64% of children while 30% had DXA Z-score between −1 and −2 and 6% had low BMD with DXA Z-score of <−2. Follow-up DXA scans at 1, 2 and 3 years interval revealed deterioration rates of 2, 43 and 75% respectively. The main determinant of BMAD was FEV1, BMI and height. Calcium intake or vitamin D level did not influence BMAD.

Conclusion: Low BMAD was present in a significant proportion of children and adolescents with CF independent of age or sex. BMAD depended on pulmonary function, height and BMI. This study highlights the importance of earlier and more regular monitoring of BMD in children with CF to help prevent deterioration of their bones.