Efficiency of quantitative ultrasound measurements as compared with dual-energy X-ray absorptiometry in the assessment of corticosteroid-induced boneimpairment

Bone loss due to corticosteroid treatment differs from that of postmenopaus al osteoporosis with regard to bone structure. Corticosteroids affect both horizontal and vertical trabeculae while horizontal trabeculae are damaged in postmenopausal osteoporosis. Dual-energy X-ray absorptiometry (DXA) is t he gold standard to evaluate bone loss. The place of quantitative ultrasoun d (QUS), a technique that could theoretically provide information on bone s tructure, is not well established in corticosteroid-induced bone impairment . The aim of the study was to determine the usefulness of QUS in the assess ment of corticosteroid-induced bone impairment. We hypothesized that the re lationship between QUS and DXA could be influenced by changes in bone struc ture and thus differ with regard to corticosteroid treatment. Seventy-seven women with inflammatory diseases chronically treated with corticosteroids (dose: 7.5-15 mg/day), 29 without corticosteroids and 100 controls were inv estigated. Bone mineral density at the lumbar spine (BMDL) was measured by DXA and QUS parameters were measured at the calcaneus. Both the QUS paramet ers (SOS, BUA, Stiffness) and BMDL were significantly lower (by 1.3% for SO S, 5.8% for BUA, 12.7% for Stiffness and 11% for BMDL) in patients treated with corticosteroids compared with patients not taking corticosteroids and with controls (p<0.001, ANCOVA, with age and height as covariates). Multipl e linear regressions of Stiffness, SOS and BUA as dependent variables on ag e, BMDL, corticosteroid treatment and a computed new variable designed to t est the interaction between BMDL and the treatment group showed that Stiffn ess, SOS and BUA were dependent on age and BMDL (p<0.001); BUA and Stiffnes s were dependent on treatment group. Taking into account the age of the pat ients, a significant difference was observed in the relation between BUA an d BMDL according to treatment with corticosteroids. A similar difference wa s found in the subgroup of patients without fractures. SOS and BUA were str ongly correlated but their relation did not differ according to treatment. Thus, QUS is useful in the assessment of corticosteroid-associated bone los s. Furthermore, the observation of a significant difference in the relation ship between BUA and BMDL with regard to corticosteroid treatment might sup port the hypothesis that QUS, especially BUA, could give additional informa tion about bone structure.