Prognostic value of inhibitory anti-ADAMTS13 antibodies in adult-acquired thrombotic thrombocytopenic purpura.

In order to assess the prognostic value of inhibitory anti-ADAMTS13 antibodies in thrombotic thrombocytopenic purpura (TTP), we performed a multicentre prospective study of 33 adult patients with idiopathic acquired TTP. Patients were treated with high-dose plasma infusion and therapeutic plasma exchange. Patients without (group 1, n = 12) and with (group 2, n = 21) detectable inhibitory anti-ADAMTS13 antibodies were compared for clinical presentation, treatment and outcome. Both groups were comparable for clinical presentation. All patients in group 1 achieved a sustained complete remission within a median of 7 d [95% confidence interval (CI), 4–18], which required a median plasma volume of 235 ml/kg (range, 131–1251). In group 2, 17 patients achieved a durable complete remission within a median of 23 d (95% CI, 11–32) ( P = 0·001). Median plasma volume was 718 ml/kg (range, 219–3107) ( P = 0·02). In group 2, there was a trend for more episodes of flare-up than in group 1 (13 vs. 3, respectively, P = 0·07). Four patients, all from group 2, died ( P = not significant). The relapse rate was comparable between both groups. We suggest that TTP with detectable inhibitory anti-ADAMTS13 antibodies displays a worse prognosis, relative to a delayed platelet count recovery, a higher plasma volume requirement to achieve complete remission, and a trend for more frequent episodes of flare-up. [ABSTRACT FROM AUTHOR]