Evaluation of bone mineral density in cystic fibrosis patients

Patients with cystic fibrosis (CF) have an increasing life span and osteoporosis has become a more recognised problem in these patients. The pathogenesis of low bone mineral density (BMD) in CF seems to be multifactorial and the aim of this study was to assess the prevalence of low BMD in a group of CF outpatients and to relate the findings with the variables studied. The study included 22 patients aged between 14 and 45 years (mean age 26.3). Two of the subjects were lung transplant patients. BMD was assessed by dual-energy X-ray absorptiometry (DEXA) at the lumbar spine (LS) and femoral neck (FN). This data was correlated with serum 25-hydroxy vitamin D (25-OHD) levels, BMI and the forced expiratory volume in one second (FEV1). BMD (Z-score and T-score) ranged from 0.6 to -6 and from 0.5 to -6.7 at LS; at FN the scores ranged from 0.6 to -3.9 and from 0.6 to -4.1. The mean serum 25-OHD concentration (12,57 ng/ml) was at the low end of the normal range (10-60 ng/ml). On average patients did not present with malnutrition, however BMI ranged from 15.2 to 33.7 kg/m2. Lung function status was assessed by FEV1; 64% of patients had FEV1 below 80% and within this group four patients had a FEV1 under 40%. There was a positive correlation between low BMD and 25-OHD concentrations and also between BMD and FEV1. There was no linear correlation between BMD and BMI.