URINARY-EXCRETION OF THE PYRIDINIUM CROSS-LINKS OF COLLAGEN IN SYSTEMIC LUPUS-ERYTHEMATOSUS

The aim of this study was to measure the urinary excretion of the pyri dinium cross-links of collagen and to determine their usefulness as ma rkers of reduced bone mineral density in systemic lupus erythematosus (SLE). All female SLE patients managed at a single centre were invited to participate in a cross-sectional study of urinary pyridinium cross -links excretion (HPLC), bone mineral density (DXA), and SLE-related v ariables. Ninety-one women with SLE were studied, 35 of whom were post menopausal. Pyridinoline/Creatinine (Pyd/Cr) and deoxypyridinoline/Cr (Dpd/Cr) levels in postmenopausal women were significantly increased c ompared with premenopausal values (p = 0.010 and p = 0.004, respective ly). Univariate linear regression analysis revealed a significant asso ciation of Dpd/Cr with reduced femoral neck and lumbar spine BMD (p = 0.001, p<0.001), and of Pyd/Cr with reduced femoral neck BMD (p = 0.02 0). In addition, the association of Pyd/Cr with reduced lumbar spine B MD approached significance (p = 0.055). Stepwise multiple linear regre ssion analysis adjusting for other variables confirmed a significant a ssociation of Dpd/Cr with reduced lumbar spine BMD (p = 0.006), and a significant association of both Pyd/Cr and Dpd/Cr with postmenopausal status (p = 0.003, p <0.001). It was concluded that in this SLE popula tion, the urinary excretion of Dpd/Cr was a useful marker of reduced B MD at the lumbar spine. Menopausal status was a major predictor of cro ss-links excretion in SLE.