Antiprothrombin antibodies: A comparative analysis of homemade and commercial methods. A collaborative study by the Forum Interdisciplinare per la Ricerca nelle Malattie Autoimmuni (FIRMA)

Angela Tincani, Gabriella Morozzi, Afeltra Afeltra, Cristiano Alessandri, Flavio Allegri, Onelia Bistoni, Nicola Bizzaro, Domenico Caccavo, Mauro Galeazzi, Roberto Gerli, Luigi Giovannelli, Giovanni Longobardo, Milvia Lotzniker, Fabio Malacarne, Paola Migliorini, Aurora Parodi, Francesca Pregnolato, Antonella Radice, Valeria Riccieri, Marina RuffelliRenato Alberto Sinico, Renato Tozzoli, Danilo Villalta, Roberto Marcolongo, Pierluigi Meroni

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: Prothrombin (PT) is a target for antibodies with lupus anticoagulant (LA) activity, suggesting the possible application of anti-prothrombin antibody (aPT) assays in patients with antiphospholipid syndrome (APS). Different methods - both homemade and commercial - for the detection of aPT are available, but they seem to produce conflicting results. The purpose of this study was to compare the performance of different assays on a set of well-characterized serum samples. Patients and methods: Sera were gathered from 4 FIRMA institutions, and distributed to 15 participating centres. Forty-five samples were from patients positive for LA and/or anticardiolipin antibodies (aCL) with or without APS, and 15 were from rheumatoid arthritis (RA) patients negative for antiphospholipid antibodies. The samples were evaluated for IgG and IgM antibodies using a homemade direct aPT assay (method 1), a homemade phosphatidylserine-dependent aPT assay (aPS/PT, method 2), and two different commercial kits (methods 3 and 4). In addition, a commercial kit for the detection of IgG-A-M aPT (method 5) was used. Results: Inter-laboratory results for the 5 methods were not always comparable when different methods were used. Good inter-assay concordance was found for IgG antibodies evaluated using methods 1, 3, and 4 (Cohen k > 0.4), while the IgM results were discordant between assays. In patients with thrombosis and pregnancy losses, method 5 performed better than the others. Conclusion: While aPT and aPS/PT assays could be of interest from a clinical perspective, their routine performance cannot yet be recommended because of problems connected with the reproducibility and interpretation of the results.

Original languageEnglish
Pages (from-to)268-274
Number of pages7
JournalClinical and Experimental Rheumatology
Volume25
Issue number2
Publication statusPublished - Mar 2007

Keywords

  • Anticardiolipin antibodies
  • Antiphospholipid antibodies
  • Antiphospholipid syndrome
  • Antiprothrombin antibodies
  • Lupus anticoagulant

ASJC Scopus subject areas

  • Rheumatology
  • Immunology

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