title: Validation of a panel of ADAMTS13 assays for diagnosis of thrombotic thrombocytopenic purpura: activity, functional inhibitor, and autoantibody test.
abstract: BACKGROUND
  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 <10%. Inhibitor assays performed with the kits showed 95% overall agreement with the reference method. A modification of the TECHNOZYM(®) autoantibody assay showed 85% overall agreement with the reference method with imprecision approximately 20%.
  
  
  CONCLUSIONS
  ADAMTS13 activity and inhibitor tests using ACTIFLUOR(™) reagents and modified TECHNOZYM(®) autoantibody ELISA showed superior performance compared to the other kits for clinical use in this study.
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: M O
authors.initials: MO
authors.lastname: Nakashima
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: H J
authors.initials: HJ
authors.lastname: Rogers
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: L
authors.initials: L
authors.lastname: Vengal
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: B
authors.initials: B
authors.lastname: Gibson
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Daly
authors.affiliation: Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA. marchak@ccf.org.
authors.forename: K
authors.initials: K
authors.lastname: Kottke-Marchant
mesh_terms: D000071120:ADAMTS13 Protein / Q000037:antagonists & inhibitors*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011480:Protease Inhibitors / Q000097:blood*; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood / Q000175:diagnosis; D011933:Reagent Kits, Diagnostic
chemical_list: D001323:Autoantibodies; D011480:Protease Inhibitors; D011933:Reagent Kits, Diagnostic; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human
keywords: ADAMTS13; TTP; thrombotic thrombocytopenic purpura