Plasma ADAMTS-13 activity in proliferative lupus nephritis: a large cohort study from China

Objectives The aim of this study was to investigate plasma ADAMTS-13 activity in patients with proliferative lupus nephritis and to evaluate the role of clinical, laboratory and pathological features, especially the vascular lesions in lupus nephritis. Methods Plasma samples from 163 class III and IV lupus nephritis patients confirmed by biopsy examinations and 98 normal controls were collected. ADAMTS-13 activity was evaluated by a residual collagen binding assay. IgG autoantibodies against ADAMTS-13 were detected by ELISA using recombinant ADAMTS-13 as a solid-phase ligand. Levels of vWF were measured by ELISA. Their associations with clinical, laboratory and pathological features were further assessed. Results Plasma ADAMTS-13 activity in lupus nephritis patients was significantly lower than that in normal controls (8421% vs. 90 +/- 13%, p=0.005). IgG ADAMTS-13 autoantibodies were detected in only three patients. The plasma level of vWF was significantly higher in the lupus nephritis group than in normal controls (1.00 +/- 0.79 vs. 0.70 +/- 0.30, p=0.025). Plasma ADAMTS-13 activity was negatively correlated with the level of serum creatinine and proteinuria (r=-0.354, p<0.001; r=-0.200, p=0.011, respectively). Patients with a higher level of ADAMTS-13 activity had significantly higher levels of factor H (401.51 +/- 183.01 mu g/ml vs. 239.02 +/- 155.45 mu g/ml, p=0.005). Plasma ADAMTS-13 activity was negatively associated with total pathological AI scores (r=-0.326, p<0.001), endocapillary hypercellularity (r=-0.419, p<0.001), cellular crescents (r=-0.274, p<0.001), subendothelial hyaline deposits (r=-0.266, p=0.001), interstitial inflammatory cell infiltration (r=-0.304, P<0.001), tubular atrophy (r=-0.199, p=0.011), acute glomerular vascular lesions (r=-0.344, p<0.001) and acute renal vascular lesions (r=-0.338, p<0.001). No association was found between level of vWF and plasma ADAMTS-13 activity (r=0.033, p=0.671). Low level of ADAMTS-13 activity was a risk factor for renal outcomes (p=0.039, HR=0.047, 95% CI: 0.120-1.005). Conclusions Decreased ADAMTS-13 activity was found in patients with proliferative lupus nephritis, and plasma ADAMTS-13 activity was closely associated with renal injury indices, especially pathological vascular scores. The role of ADAMTS-13 in the disease remains to be further investigated.