Download PDF
CC BY 4.0 · TH Open 2025; 09: a25425358
DOI: 10.1055/a-2542-5358
Case Report

Problem Solved? An Individual Ratio between Point-of-Care and Venous International Normalized Ratio Values in Two Patients with Antiphospholipid Syndrome: Two Case Reports

Bettina C. Geertsema-Hoeve
1   Division Internal Medicine and Dermatology, Department of Clinical Immunology and Rheumatology, University Medical Center Utrecht, Utrecht, The Netherlands
,
Massimo Radin
2   Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
,
Savino Sciascia 
2   Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
,
Rolf T. Urbanus
3   Division Laboratories, Pharmacy and Medical Sciences, Central Diagnostic Laboratory, University Medical Center Utrecht, Utrecht, The Netherlands
,
Albert Huisman 
3   Division Laboratories, Pharmacy and Medical Sciences, Central Diagnostic Laboratory, University Medical Center Utrecht, Utrecht, The Netherlands
,
Josine Borgsteede-de Wilde
1   Division Internal Medicine and Dermatology, Department of Clinical Immunology and Rheumatology, University Medical Center Utrecht, Utrecht, The Netherlands
,
Maarten Limper
1   Division Internal Medicine and Dermatology, Department of Clinical Immunology and Rheumatology, University Medical Center Utrecht, Utrecht, The Netherlands
› Author Affiliations
› Further Information
Also available at
   Permissions and Reprints

Abstract

Antiphospholipid syndrome (APS) is a rare autoimmune disorder characterized by thromboembolic and obstetric complications in the presence of persistent antiphospholipid antibodies (aPL). Treatment aims to prevent recurrent thrombosis, primarily using anticoagulation therapy with vitamin K antagonists (VKA). Monitoring of VKA therapy relies on the International Normalized Ratio (INR), which can be assessed using point-of-care testing (POCT). However, in a subset of APS patients with a high-risk aPL profile, the POCT-INR is falsely elevated, which might lead to underdosing of VKA and subsequent high risk of recurrent thrombosis. This case report describes two female patients with triple-positive thrombotic APS receiving VKA therapy. Both patients underwent biweekly paired INR measurements via POCT-INR and venous INR methods. Despite significant discrepancies, a strong individual linear correlation was observed: r = 0.77 (95% confidence interval [CI]: 0.54–0.99, p < 0.001) and r = 0.93 (95% CI: 0.88–0.97, p < 0.001), respectively. These findings suggest that individualized correction factors could be developed to improve the accuracy of POCT-INR measurements, thereby optimizing VKA dosing in these patients.

Keywords

antiphospholipid syndrome - International Normalized Ratio - point-of-care testing - vitamin-k antagonists - case report

Authors' Contributions

B.G. wrote the case report. M.R. and SS contributed clinical details and revisions, J.B. provided the patient perspective and statistical input, A.H. contributed laboratory details en revisions, R.U. contributed revisions, and M.L. supervised the project.




Publication History

Received: 16 January 2025

Accepted: 18 February 2025

Accepted Manuscript online:
20 February 2025

Article published online:
19 March 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

Georg Thieme Verlag KG
Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

Bibliographical Record
Bettina C. Geertsema-Hoeve, Massimo Radin, Savino Sciascia, Rolf T. Urbanus, Albert Huisman, Josine Borgsteede-de Wilde, Maarten Limper. Problem Solved? An Individual Ratio between Point-of-Care and Venous International Normalized Ratio Values in Two Patients with Antiphospholipid Syndrome: Two Case Reports. TH Open 2025; 09: a25425358.
DOI: 10.1055/a-2542-5358
 

  • References

  • 1 Barbhaiya M, Zuily S, Naden R. et al; ACR/EULAR APS Classification Criteria Collaborators. The 2023 ACR/EULAR antiphospholipid syndrome classification criteria. Arthritis Rheumatol 2023; 75 (10) 1687-1702
    Search in Google Scholar
  • 2 Knight JS, Branch DW, Ortel TL. Antiphospholipid syndrome: advances in diagnosis, pathogenesis, and management. BMJ 2023; 380: e069717
    Search in Google Scholar
  • 3 Limper M, de Leeuw K, Lely AT. et al. Diagnosing and treating antiphospholipid syndrome: a consensus paper. Neth J Med 2019; 77 (03) 98-108
    Search in Google Scholar
  • 4 Shikdar S, Vashisht R, Bhattacharya PT. International Normalized Ratio (INR). Treasure Island (FL): StatPearls Publishing LLC; 2024
    Search in Google Scholar
  • 5 Gardiner C, Williams K, Mackie IJ, Machin SJ, Cohen H. Patient self-testing is a reliable and acceptable alternative to laboratory INR monitoring. Br J Haematol 2005; 128 (02) 242-247
    Search in Google Scholar
  • 6 Noordermeer T, Urbanus RT, Wong CY. et al. Interference in point-of-care international normalized ratio monitoring in patients with lupus anticoagulant is correlated with anti-β2-glycoprotein I antibody titers. Res Pract Thromb Haemost 2022; 7 (01) 100011
    Search in Google Scholar
  • 7 Isert M, Miesbach W, Schüttfort G. et al. Monitoring anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome. Ann Hematol 2015; 94 (08) 1291-1299
    Search in Google Scholar
  • 8 Laurent C, Ricard L, Nguyen Y. et al. Triple positive profile in antiphospholipid syndrome: prognosis, relapse and management from a retrospective multicentre study. RMD Open 2023; 9 (01) e002534
    Search in Google Scholar
  • 9 Tripodi A, Chantarangkul V, Clerici M, Negri B, Galli M, Mannucci PM. Laboratory control of oral anticoagulant treatment by the INR system in patients with the antiphospholipid syndrome and lupus anticoagulant. Results of a collaborative study involving nine commercial thromboplastins. Br J Haematol 2001; 115 (03) 672-678
    Search in Google Scholar
  • 10 Braun S, Spannagl M, Völler H. Patient self-testing and self-management of oral anticoagulation. Anal Bioanal Chem 2009; 393 (05) 1463-1471
    Search in Google Scholar
  • 11 Horsti J. Comparison of quick and Owren prothrombin time with regard to the harmonisation of the international normalised ratio (INR) system. Clin Chem Lab Med 2002; 40 (04) 399-403
    Search in Google Scholar
  • 12 Meijer P, Kynde K, van den Besselaar AMHP, Van Blerk M, Woods TAL. International normalized ratio (INR) testing in Europe: between-laboratory comparability of test results obtained by Quick and Owren reagents. Clin Chem Lab Med 2018; 56 (10) 1698-1703
    Search in Google Scholar
  • 13 Osman A, Lindahl TL. Plasma predilution with addition of depleted plasma in a prothrombin time reagent improves the agreement between different prothrombin time methods. Scand J Clin Lab Invest 2009; 69 (03) 395-400
    Search in Google Scholar
  • 14 Della Valle P, Crippa L, Garlando AM. et al. Interference of lupus anticoagulants in prothrombin time assays: implications for selection of adequate methods to optimize the management of thrombosis in the antiphospholipid-antibody syndrome. Haematologica 1999; 84 (12) 1065-1074
    Search in Google Scholar
  • 15 Noordermeer T, Molhoek JE, Schutgens REG. et al. Anti-β2-glycoprotein I and anti-prothrombin antibodies cause lupus anticoagulant through different mechanisms of action. J Thromb Haemost 2021; 19 (04) 1018-1028
    Search in Google Scholar