ADAMTS13 and Thrombocytopenia: Regarding the laboratory parameters at the time of presentation of the acute TMA event, only platelet counts were significantly different between the two patient groups, a severe thrombocytopenia (count < 30 × 109/l) being present in almost all patients with severe ADAMTS13 deficiency and in only 25% of those with ADAMTS13 ≥ 10%.