Plasma levels of HNP1-3 and subtypes (HNP1, HNP2, and HNP3) in patients with acquired autoimmune TTP. (A) Plasma levels of HNP1-3 in patients with acquired autoimmune TTP and healthy controls as determined by ELISA. (B-E) The plasma levels of HNP1, HNP2, HNP3, and total HNP1+2+3, respectively, in patients with acquired autoimmune TTP and healthy controls as determined by LC-MS/MS. The relative abundance of HNP1, HNP2, and HNP3 in TTP patients was determined by comparing with that in the mean value of each HNP in normal human plasma (defined as having 1 AU/mL). (F) The Spearman rank correction coefficient (ρ = 0.7932) between LC-MS/MS and ELISA for measurement of total plasma levels of HNP1-3 using GraphPad Prism 6. P values <.05 and .01 are considered to be statistically significant and highly significant.