Clinical performance of the assay was assessed using plasma samples of patients who (i) developed transplant‐associated thrombotic microangiopathy [n = 10; median age 14 years (range 3–19)], (ii) had reduced ADAMTS13 activity [n = 6; median age 16 years (range 9–18)], and (iii) developed acquired Von‐Willebrand disease [n = 10; median age 18.5 years (range 0.5–18)]. This evidence concerns the gene ADAMTS13 and thrombotic microangiopathy.