Validation of a panel of ADAMTS13 assays for diagnosis of thrombotic thrombocytopenic purpura: activity, functional inhibitor, and autoantibody test

Summary Introduction Quantitation of ADAMTS13 activity, functional inhibitors, and autoantibodies is crucial in diagnosis and management of thrombotic thrombocytopenic purpura. We compared and optimized commercial assay kits and validated a testing panel. Methods Citrated plasma specimens from healthy volunteers and residual samples submitted for clinical testing were used in the study. Commercially available ADAMTS13 activity assays including ACTIFLUOR™ ADAMTS13 (Sekisui Diagnostics, Stamford, CT, USA), LIFECODES ATS-13 (Gen-Probe Inc., San Diego, CA, USA), and TECHNOZYM® ADAMTS-13 (Technoclone, Vienna, Austria) were evaluated. Functional inhibitor assays were performed using internally developed mixing protocols. Two autoantibody assays were also evaluated: IMUBIND® (Sekisui Diagnostics) and TECHNOZYM® ADAMTS-13 INH ELISA kits (Technoclone). Results A laboratory-developed assay using ACTIFLUOR™ reagents showed best agreement with the reference method, and full validation showed a reportable range of 5% (LLOQ) to 114% with a reference interval of ≥68%. Both intra- and interassay coefficients of variation were