ADAMTS13 and thrombotic thrombocytopenic purpura: Coppo et al. reported that either a platelet count ≤ 30 × 109 L−1, creatinine level of ≤ 200 μmol L−1, or positive ANA has a 85% positive predictive value and 93.3% negative predictive value for severe ADAMTS‐13 deficiency in a large TTP/TMA cohort.