Laboratory testing for factor inhibitors

Authors

  • E. J. Favaloro,

    Corresponding author
    1. Diagnostic Haemostasis, Haematology Department, Institute of Clinical Pathology and Medical Research (ICPMR), Pathology West, Westmead Hospital, Westmead, NSW, Australia
    • Correspondence: E. J. Favaloro, Diagnostic Haemostasis, Haematology Department, Institute of Clinical Pathology and Medical Research (ICPMR), Pathology West, Westmead Hospital, Westmead, NSW, Australia.

      Tel.: +612 9845 5161 (Office/Messages), +612 9845 6618 (Laboratory); fax: +612 9689 2331;

      e-mail: emmanuel.favaloro@health.nsw.gov.au

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  • B. Verbruggen,

    1. ECAT Foundation, Leiden, The Netherlands
    2. Laboratory of Clinical Chemistry and Haematology, Jeroen Bosch Hospital, sHertogenbosch, The Netherlands
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  • C. H. Miller

    1. Division of Blood Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA, USA
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Summary

Inhibitor assays are performed when patients present with unexplained prolonged routine coagulation test times and unexpected and/or unusual bleeding (potential for acquired haemophilia) as well as being a part of normal congenital haemophilia management and monitoring, particularly when bleeding occurs on therapy, or when increments in factor levels post-factor replacement remain lower than expected. In this article, we will describe the assays used, as well as their development, pitfalls in testing such as inter-laboratory variability and false negative/positive results, as well as some strategies for overcoming these pitfalls and potential alternative test approaches. The inter-laboratory coefficient of variation often approaches (and sometimes exceeds) 50%, as evidenced by various external quality assessment groups, and this variability has not improved over recent years. Additional important considerations include appropriate interpretation of test results, repeat testing for confirmation, and assessment of recovery as part of the diagnostic process.

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