Discrepancies in international normalized ratio measurement in a patient after aortic valve replacement as a lupus anticoagulant indicator: a diagnostic and therapeutic problem (a case report)

Résumé fourni par la source

Introduction . Vitamin K antagonist therapy monitoring using the international normalized ratio (INR) is the standard for patient management after aortic valve replacement. Lupus anticoagulant (LA) can lead to false changes in the INR value depending on the reagent composition, which creates a risk of iatrogenic complications. Brief description . A 61-year-old patient with a history of aortic valve replacement and two episodes of ischemic stroke demonstrated significant INR discrepancies across laboratories, limiting the ability to reliably assess the adequacy of warfarin anticoagulation therapy and its safety profile. Further testing using thromboplastin of different origins (recombinant and rabbit brain tissue) in the INR assay reagent and a mixed assay revealed differences in the assay system sensitivity to the interfering factor. The combination of persistent discrepancies in the mixed assay and consistently higher INR values with recombinant thromboplastin served as indirect evidence of LA influence. INR values obtained using tissue thromboplastin, as less sensitive to LA, were used for subsequent therapy monitoring. Conclusion . This case demonstrates the importance of understanding the influence of preanalytical and analytical factors, particularly LA, on INR results. When unexplained or conflicting results are obtained in patients at high thrombotic risk, a personalized laboratory approach is necessary, including reagent comparison, a mixing test, and additional testing to detect LA. Identifying the interference cause allows for the selection of an appropriate monitoring strategy and the prevention of adverse consequences for the patient.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.