title: Evaluation of a chromogenic commercial assay using VWF-73 peptide for ADAMTS13 activity measurement.
abstract: BACKGROUND
  Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA), related to a severe functional deficiency of ADAMTS13 activity (<10% of normal). ADAMTS13 activity is thus crucial to confirm the clinical suspicion of TTP, to distinguish it from other TMAs, and to perform the follow-up of TTP patients.
  
  
  METHODS
  We compared the performance of the commercial chromogenic assay Technozym ADAMTS13 Activity ELISA (chromogenic VWF73 substrate, Chr-VWF73, Technoclone, Vienna, Austria), to that of our in-house FRETS-VWF73 used as reference method. A large group of 247 subjects (30 healthy volunteers and 217 patients with miscellaneaous TMAs) was studied.
  
  
  RESULTS
  The lower limit of detection of the Chr-VWF73 was 3%, which is well adapted to the clinically relevant threshold for TTP diagnosis (10%). Our results showed a reasonable agreement between FRETS-VWF73 and Chr-VWF73 assays to distinguish samples with an ADAMTS13 activity <10% from those with an ADAMTS13 activity >10%. However, Chr-VWF73 assay provided false negative results in ~12% of acute TTP patients. Inversely, the Chr-VWF73 assay globally underestimated ADAMTS13 activity in detectable values ranging from 11 to 100% (with a great variability compared to FRETS-VWF73), which may be a concern for the follow-up of TTP patients in remission.
  
  
  CONCLUSIONS
  In-house assays developed and performed by expert laboratories remain the reference methods that should be used without limitation to control values provided by commercial assays when needed. Also, the development of an international reference preparation will be crucial to improve standardization.
authors.affiliation: Service d'Hématologie biologique, Hôpital Antoine Béclère, Assistance Publique-Hôpitaux de Paris, Clamart, Université Paris 11, France.
authors.forename: Bérangère
authors.initials: B
authors.lastname: Joly
authors.affiliation: Service d'Hématologie biologique, Hôpital Louis Mourier, Assistance Publique-Hôpitaux de Paris, Colombes, Université Paris 7, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Stepanian
authors.affiliation: Département d'épidémiologie et de recherche clinique, Hôpital Louis Mourier, Assistance Publique-Hôpitaux de Paris, Colombes, Université Paris 7, France.
authors.forename: David
authors.initials: D
authors.lastname: Hajage
authors.affiliation: Service d'Hématologie biologique, Hôpital Antoine Béclère, Assistance Publique-Hôpitaux de Paris, Clamart, Université Paris 11, France; French Reference Center for Thrombotic Microangiopathies (CNR-MAT), Hôpital Saint Antoine, Assistance Publique-Hôpitaux de Paris, Paris, Université Paris 6, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Thouzeau
authors.affiliation: Service d'Hématologie biologique, Hôpital Antoine Béclère, Assistance Publique-Hôpitaux de Paris, Clamart, Université Paris 11, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Capdenat
authors.affiliation: French Reference Center for Thrombotic Microangiopathies (CNR-MAT), Hôpital Saint Antoine, Assistance Publique-Hôpitaux de Paris, Paris, Université Paris 6, France; Service d'Hématologie, Hôpital Saint Antoine, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Coppo
authors.affiliation: Service d'Hématologie biologique, Hôpital Antoine Béclère, Assistance Publique-Hôpitaux de Paris, Clamart, Université Paris 11, France; French Reference Center for Thrombotic Microangiopathies (CNR-MAT), Hôpital Saint Antoine, Assistance Publique-Hôpitaux de Paris, Paris, Université Paris 6, France. Electronic address: agnes.veyradier@abc.aphp.fr.
authors.forename: Agnès
authors.initials: A
authors.lastname: Veyradier
mesh_terms: D051722:ADAM Proteins / Q000032:analysis / Q000378:metabolism*; D000071120:ADAMTS13 Protein; D004797:Enzyme-Linked Immunosorbent Assay; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D057230:Limit of Detection; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011697:Purpura, Thrombotic Thrombocytopenic / Q000175:diagnosis* / Q000378:metabolism; D015203:Reproducibility of Results; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010455:Peptides; D014841:von Willebrand Factor; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human
keywords: ADAMTS13; ADAMTS13 activity; Chr-VWF73; FRETS-VWF73; Thrombotic thrombocytopenic purpura