Blood yield stress in systemic sclerosis

Blood is a weak percolating physical gel at low shear rates, in which clust ers of aggregates can be reversibly disaggregated or formed again. This phe nomenon is of potential importance in the microvascular pathophysiology of ischemic and vasospastic disorders such as systemic sclerosis. The aim of t his work was to determine blood yield stress using low-shear-rate rheometry with a homemade roughened Couette device in 10 patients with systemic scle rosis compared with 10 healthy controls. Biochemical plasmatic parameters w ere assessed independently. Results showed a significantly increased stress (+56%, P < 0.05 at 60% hematocrit) for scleroderma patients. The best bioc hemical predictor for yield stress was the ratio of albumin to globulins; 6 9% of its variance was explained by plasmatic factors (albumin, fibrinogen, and globulins) in scleroderma patients and 23.4% in healthy controls. Addi tional microscopic observations showed different microstructures. These res ults support the hypothesis of an abnormal red blood cell organization proc ess in scleroderma patients that could be partly responsible for the severi ty of ischemic complications of the disease.