289.1 Evaluation of a rapid screening test as an effective tool in decentralizing ADAMTS13 activity testing - report from the rapid assessment of plasma in microangiopathic thrombocytopenia (RAPMAT) study

Background: Thrombotic thrombocytopenia purpura (TTP) is a rare life-threatening disease and timely diagnosis is critical. An ADAMTS13 activity level of < 10 IU/dl is used to differentiate TTP from other thrombotic microangiopathic thrombocytopenia (TMAT) diagnosis. Current test iterations based on FRET, ELISA or chemiluminescence assays are time consuming, have long turnaround times or are not readily available. Aims: To evaluate and compare a rapid flow through screening test (Technoclone, Vienna) against a VWF73 ADAMTS13 activity ELISA (Technoclone, Vienna) and an ADAMTS13 automated chemiluminescence method (Acustar - Werfen). Methods: De- identified suspect and confirmed TTP plasmas (n = 120) from 6 diagnostic laboratories in Australia and New Zealand were collected. Study was approved by MU HREC for assay development and calibration (Permit No. 2013/131). Local and central measurement of ADAMTS13 activity level comparison was made with the flow through test and functional ELISA assay. Additionally, the central study site also included a chemiluminescence method. The semi quantitative screening test assigns ADAMTS13 to one of four level indicator guides: 0, 10, 40 and 80 IU/dl. Results: ADAMTS13 activity levels from local and central study sites were comparable, (r2 = 0.78) as was the correlation with the chemiluminescence and ELISA methods (r2 = 0.86). All but 1 of the rapid flow through results confirmed the quantitative ELISA results of <10 IU/dl, the TTP diagnostic threshold. There were 2 results of 40 IU/dl that were <10 IU/dl by the ELISA assay and no results at 80 IU/dl resulted in activity levels less than