Laboratory Assessment of Factor VIII Inhibitor Titer : The North American Specialized Coagulation Laboratory Association Experience

• Published in: American journal of clinical pathology Vol. 131; no. 4; pp. 552 - 558
• Main Authors: PEERSCHKE, Ellinor I. B, CASTELLONE, Donna D, LEDFORD-KRAEMER, Marlies, VAN COTT, Elizabeth M, MEIJER, Piet
• Format: Journal Article
• Language: English
• Published: Chicago, IL American Society of Clinical Pathologists 01.04.2009
• Subjects: Autoantibodies - blood; Biological and medical sciences; Factor VIII - immunology; Factor VIII - therapeutic use; Hematologic and hematopoietic diseases; Hematologic Tests - methods; Hematologic Tests - standards; Hemophilia A - blood; Hemophilia A - drug therapy; Hemophilia A - immunology; Humans; Investigative techniques, diagnostic techniques (general aspects); Laboratories, Hospital - standards; Medical sciences; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Platelet diseases and coagulopathies; Quality Control; Sensitivity and Specificity; United States; North America; America; North American Specialized Coagulation Laboratory Association; Blood coagulation; NASCOLA; American; Factor VIII; Coagulation; Hemopathy; Laboratory; Medical screening; Genetic disease; Factor VIII inhibitor titer; ECAT; Anatomic pathology; Association; Laboratory investigations; Proficiency testing; Hemophilia; Inhibitor; Coagulation factor; Coagulopathy
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1309/AJCPMKP94CODILWS

Quantification of inhibitory antibodies against infused factor VIII (FVIII) has an important role in the management of patients with hemophilia A. This article summarizes results from the largest North American FVIII inhibitor proficiency testing challenge conducted to date. Test samples, 4 negative and 4 positive (1-3 Bethesda units [BU]/mL), were distributed by the ECAT Foundation in conjunction with the North American Specialized Coagulation Laboratory Association and analyzed by 38 to 42 laboratories in 2006 and 2007. Whereas laboratories were able to distinguish between the absence and presence of low-titer FVIII inhibitors, the intralaboratory coefficient of variation was high (30%-42%) for inhibitor-positive samples, and the definition of lower detection limits of the assay was variable (0-1 BU/mL). Most laboratories performed the Bethesda assay with commercially supplied buffered normal pooled plasma in a 1:1 mix with patient plasma. These data provide information for the development of consensus guidelines to improve FVIII inhibitor quantification.