The Oklahoma Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome (TTP-HUS) Registry: a community perspective of patients with clinically diagnosed TTP-HUS.

The Oklahoma Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome (TTP-HUS) Registry enrolls all consecutive patients for whom plasma exchange treatment is requested for clinically diagnosed TTP-HUS within a defined geographic region. During 14.5 years, from January 1, 1989 until June 30, 2003, 301 patients have been enrolled; follow-up is complete on 300 patients. Clinical categories have been designated based on associated conditions and potential etiologies; presenting features and clinical outcomes have been defined to allow comparisons between groups. ADAMTS-13 activity was measured on 142 (88%) of 161 consecutive patients enrolled from 1995 to 2001. Only 13% of all patients, and 33% of patients with idiopathic TTP-HUS, had severe ADAMTS-13 deficiency (<5% activity). The presenting features and clinical outcomes of patients with severe ADAMTS-13 deficiency were heterogeneous and not distinct from patients without severe ADAMTS-13 deficiency. These data suggest that severe ADAMTS-13 deficiency does not detect all patients who may be appropriately diagnosed with TTP-HUS and who may respond to plasma exchange treatment. Prospective data from consecutive patients are essential to translate new observations on pathogenesis into improved patient care.