Anti-ADAMTS13 antibody features (IG isotype titers, functional ADAMTS13 inhibitor and circulating immune complexes [CIC]) in patients with acquired thrombosis thrombocitopenic purpura (ATTP) at first consultation in our institution.

KEMPFER AC; PAIVA J; SANCHEZ LUCEROS A; ALBERTO F; WOODS AI; CASINELLI MM; LAZZARI MA

Toronto

Congreso; XXV ISTH Congress; 2015

isth

Background: aTTP form is often caused by circulating antibody (ab). The formation of CIC may be a pathophysiologic mechanism in aTTP.Aims: To evaluate the relationship of ADAMTS13-measurements in 40 patients(P), 28 in acute phase (ap) and 12 non acute phase (nap).Methods: ADAMTS13 activity (act), antigen (ag) and Free IgG anti-ADAMTS13 ab (free IgG ab) were evaluated by ELISA kits. Functional ADAMTS13 inhibitor (FI) was detected as Ferrari(2007) described. Detection of CIC by coimmunoprecipitation (WB) and ELISA with rabbit anti-ADAMTS13 (ABCAM).Informed consent and ethical approval were obtained.Results: In ap, act was severely reduced in 26/28P (93%) and reduced in 2/28P(7%). Within 26P Ag was undetectable in 7(27%), severely reduced in 3(11%) and reduced in 14(54%). FI was positive in 24/28P(86%). Free IgG ab was positive in 24/28P(86%).In nap, act was severely reduced in 3/12P(25%) and reduced in 6/12P(50%). Within those 12P, ag was severely reduced in 1(8%) and reduced in 6(50%). FI was positive in 8/11P(73%). Free IgG ab was positive in 10/12P(83%). Both Free IgM ab and IgA ab were positive in 1/12P(8%).The capturing ab for CIC showed good sensitivity when tested using a P with a CIC of cut-off of 1.93 normalized OD units. The nonparametric correlation n=9, Spearman r=0.695, p