With regard to ADAMTS13 testing results, 94% of acute TMA events with severe ADAMTS13 deficiency had undetectable ADAMTS13 activity levels, a reduced ADAMTS13 antigen (< 0.6 ug/ml) and positive anti-ADAMTS13 antibodies (> 15 U/ml). This evidence concerns the gene ADAMTS13 and hyperinsulinemic hypoglycemia, familial, 4.