LAUSR

INTRODUCTION Therapeutic plasma exchange (TPE) is mainstay therapy for thrombotic thrombocytopenic purpura (TTP). However, it remains controversial if ABO type influences diagnosis or time to remission. MATERIALS AND METHODS We investigated if ABO type influences length of TPE regimen in TTP patients with ADAMTS13 deficiency at our institution. Seventy out of 71 patients with suspected TTP who had ADAMTS13 activity measured were included. ADAMTS13 activity <10% defined those with idiopathic/acquired TTP (41/70). RESULTS We found that among patients with ADAMTS13 deficiency, non-O patients required a significantly greater number of TPE (NoP) compared to O patients (p = 0.039). Additionally, patients with ADAMTS13 deficiency regardless of ABO type needed more TPE to achieve platelet recovery compared to those patients without deficiency (p = 0.00002). In regard to other variables that may affect response to therapy in TTP patients, we found no association between obesity and NoP; however, obesity rate was higher among ADAMTS13 deficient patients compared to overall obesity rate of our regional general population. Likewise, were found that blood group O did not occur with greater frequency in our cohort. CONCLUSIONS Our data indicates that ABO may affect the NoP patients required for disease remission. We found that non-O patients needed more procedures to overcome their disease. Further work with greater number of patients will be needed to determine if specific non-O blood types require more procedures to recover their platelet count.