[Activity loss of Von Willebrand factor cleaving protein (ADAMTS-13) is diagnostic for primary and pregnancy-related thrombotic thrombocytopenic purpura].

OBJECTIVE: To determine whether the measurement of the Von Willebrand factor cleaving protease ADAMTS-13, such as is carried out at the University Medical Centre of Utrecht, The Netherlands, contributes towards the diagnosis and treatment of patients with thrombotic thrombocytopenic purpura (TTP).

DESIGN: Descriptive.

METHOD: In a group of 98 patients from 21 hospitals, with a Coombs-negative haemolytic anaemia and thrombocytopenia, the ADAMTS-13 activity was measured. Treatment was given irrespective of ADAMTS-13 activity.

RESULTS: ADAMTS-13 activity was absent in 27 of 29 patients diagnosed with primary TTP and in all 5 pregnancy-TTP patients. In patients suffering from TTP after bone marrow transplantation (post-BMT) and in all other patients included in this study, ADAMTS-13 activity was normal. Of the 32 patients with absent ADAMTS-13 activity, 28 underwent plasmapheresis. This treatment proved effective as all 28 patients responded well. 17 patients with normal ADAMTS-13 activity also underwent plasmapheresis; 5 (30%) responded well to treatment. In 2 cases a final diagnosis of primary TTP was made, in a further 2, haemolytic uraemic syndrome and in 1 case sepsis was diagnosed.

CONCLUSION: In this study, the absence of ADAMTS-13 activity predicted primary TTP and TTP of pregnancy with a sensitivity of 93% and a specificity of 100%. Absence of ADAMTS-13 activity is a strong indication for plasma exchange.