Well-nourished cystic fibrosis patients have normal mineral density, but reduced cortical thickness at the forearm

Abstract

Our goal was to assess mineral density and geometry of the cortex at the level of the forearm in adolescents and young adults with cystic fibrosis, using peripheral quantitative computed tomography. We found that density was normal, but cortical thickness significantly reduced, as well in males as in females.

Introduction: Our goal was to measure bone mineral density as a volumetric density, as well as total cross-sectional area, cortical area and cortical thickness, using peripheral quantitative computed tomography (pQCT) at the forearm in adolescents and young adults with cystic fibrosis. We evaluated relationships between forearm bone measurements and body composition assessed using dual energy X-ray absorptiometry (DXA).

Methods: An XCT 2000 pQCT (Stratec, Pforzheim, Germany) and a QDR 4500 A-upgraded to Discovery DXA device (Hologic, Waltham, MA, USA) were used.

Results: Forty-eight patients (31 males,17 females, mean+/-SD 20+/5 years) were studied. Anthropometric features were: height 169+/- 10 cm, SDS 0.05+/-0.12, body mass index 19.8+/- 2.5 kg/m(2), SDS -0.56+/-0.14. Bone mineral density and total cross-sectional area of the forearm and body composition were normal, whereas cortical thickness was significantly reduced in males (mean Z-score - 1.22, p < 0.05), and in females (mean Z-score - 1.61, p < 0.05). Total body lean mass correlated more strongly with cortical thickness (r = 0.72, p < 0.001) than with total bone mineral density at the proximal radius (r = 0.39, p < 0.05).

Conclusions: Adolescents and young adults with cystic fibrosis, presenting with only a slight degree of underweight, have at the radius a preserved bone mineral density but a reduced cortical thickness.