Background Many studies using dual-energy X-ray absorptiometry (DXA) have shown that cumulative organ damage (SDI) of SLE is a risk factor for decreased areal bone mineral density (aBMD), but without indicating respective contributions of disease- and therapy-related SDI on BMD. As a 2-dimensional projectional imaging technique, DXA measures integral aBMD of cortical and trabecular bone and is confounded by bone geometry which limited its ability in predicting fracture. The high-resolutinon peripheral quantitative CT (HR-pQCT) capable of distinguishing trabecular and cortical bone compartment with low radiation has now been available in studies of bone microarchitecture.
Objectives To evaluate bone quality in Chinese female patients with SLE who were on long-term glucocorticoids (GCs) and to focus on the correlation between bone quality and organ damage, including damage related to disease itself and treatment.
Methods Seventy eight Chinese female patients with SLE damage on long-term GCs, were recruited in the cross-sectional study. Clinical parameters of interest included disease activity, SDI, major organ involvement and use of GCs and immunosuppressant were recorded. Bone microarchitecture at the non-dominant distal radius was measured by HR-pQCT.
Results Patients were with mean age (SD) of 45 (10) and 54% being postmenopausal. The median SDI score of the cohort was 1 (interquartile range: 1-2, range 1-5). In univariate analysis, body height and weight correlated with bone geometry; age, postmenopausal status and SDI negatively associated with volumetric bone mineral density (vBMD), microarchitecture. During multiple regression analysis, SDI was the only clinical variable constantly associated with deterioration of vBMD and microarchitecture. We further distinguished 2 categories of disease damage, the therapy-related damage including cataract, osteoporotic fracture, avascular necrosis and premature gonadal failure, and SLE-related damage including the organ damages listed on the SDI other than the therapy-related damage. The SDI score was then divided as 2 scores, the therapy-related SDI score (sum of the scores of therapy-related damage) and the disease-related SDI score (sum of the scores of disease-related damage). In each multivariate analysis, the coefficient for therapy-related SDI score were at least 33% larger than the one for disease-related SDI score, suggesting therapy-related damage contributed more to the deterioration of bone density and microarchitecture compared with disease-related SDI damage.
Conclusions Cumulative organ damage negatively correlated with vBMD, microarchitecture in female patients with SLE damage on long-term GCs. Therapies, such as GCs-sparing therapies or therapies without deleterious effect on bone, which can effectively control disease inflammation and, at the same time, prevent organ damage are potential in preserving bone quality in patients with SLE.
Becker A, Fischer R, Scherbaum WA, et al. Osteoporosis screening in systemic lupus erythematosus: impact of disease duration and organ damage. Lupus 2001;10:809-14.
Sornay-Rendu E, Boutroy S, et al. Alterations of cortical and trabecular architecture are associated with fractures in postmenopausal women, partially independent of decreased BMD measured by DXA: the OFELY study. J Bone Miner Res 2007;22:425-33.
Disclosure of Interest None Declared