External peer review quality assurance testing in von Willebrand disease: the recent experience of the United States College of American Pathologists proficiency testing program.
The U.S. College of American Pathologists (CAP) has conducted a focused study of the proficiency testing for von Willebrand disease (vWD) analysis from 2003 to 2005. This report summarizes the findings regarding the accuracy and precision of the various assays at different analyte levels, as well as the influence of the reference material used to construct the assay standard curve. The results show that testing of von Willebrand factor (vWF):antigen (vWF:Ag) and ristocetin cofactor activity (vWF:RCo) is reasonably accurate, with all-method mean values falling within 3.2 and 5.6%, respectively, of the International Society on Thrombosis and Haemostasis Secondary Coagulation Standard (lot 2) assigned values. vWF:Ag measurements are reasonably precise (all-method coefficients of variation [CVs] = 10.7 to 15.1%), even at lower levels of vWF. The highest precision was observed for immunoturbidometric assays (CVs, 6.3 to 9.7%). vWF:RCo measurements are less precise (all-method CVs, 23.3 to 30.9%). The reference materials used in the standard curves for immunoturbidometric vWF:Ag assays appear to have accurately assigned vWF values for the majority of commercial suppliers.
Hayes
Timothy E
TE
Department of Pathology and Laboratory Medicine, Maine Medical Center, Portland, Maine 04102, USA. hayest@mmc.org
Brandt
John T
JT
Chandler
Wayne L
WL
Eby
Charles S
CS
Kottke-Marchant
Kandice
K
Krishnan
Jayashree
J
Lefkowitz
Jerry B
JB
Olson
John D
JD
Rund
Chad R
CR
Van Cott
Elizabeth M
EM
Cunningham
Mark T
MT
D000941:Antigens / Q000097:blood*; D019411:Clinical Laboratory Techniques / Q000592:standards*; D006801:Humans; D007753:Laboratories / Q000592:standards; D010336:Pathology / Q000592:standards; D010380:Peer Review; D011785:Quality Assurance, Health Care; D014481:United States; D014842:von Willebrand Diseases / Q000175:diagnosis* / Q000473:pathology; D014841:von Willebrand Factor / Q000276:immunology
D000941:Antigens; C029417:Von Willebrand antigen; D014841:von Willebrand Factor